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 $92.67   3.237%   $95.6697   $95.67   $95.65   $95.70  
  Purchase #2 $146.62   6.401%   $156.0051   $156.01   $156.00   $156.00  
  Purchase #3 $232.97   4.419%   $243.2649   $243.26   $243.25   $243.30  
  Purchase #4 $112.42   4.798%   $117.8139   $117.81   $117.80   $117.80  
  Purchase #5 $60.39   11.625%   $67.4103   $67.41   $67.40   $67.40  
  Purchase #6 $190.95   4.838%   $200.1882   $200.19   $200.20   $200.20  
  Purchase #7 $203.56   8.144%   $220.1379   $220.14   $220.15   $220.10  
  7 purchase totals = $1,039.58       $1,100.4900   $1,100.49   $1,100.45   $1,100.50