Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $169.41   8.650%   $184.064   $184.06   $184.05   $184.10  
  Purchase #2 $103.88   8.295%   $112.4968   $112.50   $112.50   $112.50  
  Purchase #3 $112.46   11.213%   $125.0701   $125.07   $125.05   $125.10  
  Purchase #4 $188.56   10.188%   $207.7705   $207.77   $207.75   $207.80  
  Purchase #5 $211.80   11.238%   $235.6021   $235.60   $235.60   $235.60  
  Purchase #6 $106.32   3.727%   $110.2825   $110.28   $110.30   $110.30  
  Purchase #7 $243.65   5.555%   $257.1848   $257.18   $257.20   $257.20  
  7 purchase totals = $1,136.08       $1,232.4708   $1,232.46   $1,232.45   $1,232.60