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 $162.50   3.136%   $167.596   $167.60   $167.60   $167.60  
  Purchase #2 $56.59   6.654%   $60.3555   $60.36   $60.35   $60.40  
  Purchase #3 $43.77   11.437%   $48.776   $48.78   $48.80   $48.80  
  Purchase #4 $174.93   9.330%   $191.251   $191.25   $191.25   $191.30  
  Purchase #5 $233.56   6.154%   $247.9333   $247.93   $247.95   $247.90  
  Purchase #6 $167.60   5.864%   $177.4281   $177.43   $177.45   $177.40  
  Purchase #7 $194.43   11.855%   $217.4797   $217.48   $217.50   $217.50  
  7 purchase totals = $1,033.38       $1,110.8196   $1,110.83   $1,110.90   $1,110.90