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 $156.61   8.132%   $169.3455   $169.35   $169.35   $169.30  
  Purchase #2 $57.84   7.677%   $62.2804   $62.28   $62.30   $62.30  
  Purchase #3 $159.92   10.706%   $177.041   $177.04   $177.05   $177.00  
  Purchase #4 $243.67   11.266%   $271.1219   $271.12   $271.10   $271.10  
  Purchase #5 $142.72   5.775%   $150.9621   $150.96   $150.95   $151.00  
  Purchase #6 $124.28   9.860%   $136.534   $136.53   $136.55   $136.50  
  Purchase #7 $95.49   6.263%   $101.4705   $101.47   $101.45   $101.50  
  7 purchase totals = $980.53       $1,068.7554   $1,068.75   $1,068.75   $1,068.70