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 $58.52   7.582%   $62.957   $62.96   $62.95   $63.00  
  Purchase #2 $159.75   4.555%   $167.0266   $167.03   $167.05   $167.00  
  Purchase #3 $67.32   4.817%   $70.5628   $70.56   $70.55   $70.60  
  Purchase #4 $40.96   4.493%   $42.8003   $42.80   $42.80   $42.80  
  Purchase #5 $227.43   8.179%   $246.0315   $246.03   $246.05   $246.00  
  Purchase #6 $204.45   3.391%   $211.3829   $211.38   $211.40   $211.40  
  Purchase #7 $36.54   4.801%   $38.2943   $38.29   $38.30   $38.30  
  7 purchase totals = $794.97       $839.0554   $839.05   $839.10   $839.10