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 $88.35   9.757%   $96.9703   $96.97   $96.95   $97.00  
  Purchase #2 $154.97   7.231%   $166.1759   $166.18   $166.20   $166.20  
  Purchase #3 $212.90   10.700%   $235.6803   $235.68   $235.70   $235.70  
  Purchase #4 $186.31   13.243%   $210.983   $210.98   $211.00   $211.00  
  Purchase #5 $58.59   9.714%   $64.2814   $64.28   $64.30   $64.30  
  Purchase #6 $112.47   6.685%   $119.9886   $119.99   $120.00   $120.00  
  Purchase #7 $62.64   9.237%   $68.4261   $68.43   $68.45   $68.40  
  7 purchase totals = $876.23       $962.5056   $962.51   $962.60   $962.60