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 $56.69   9.437%   $62.0398   $62.04   $62.05   $62.00  
  Purchase #2 $143.75   6.149%   $152.5892   $152.59   $152.60   $152.60  
  Purchase #3 $67.60   9.818%   $74.237   $74.24   $74.25   $74.20  
  Purchase #4 $96.60   4.737%   $101.1759   $101.18   $101.20   $101.20  
  Purchase #5 $224.95   9.827%   $247.0558   $247.06   $247.05   $247.10  
  Purchase #6 $113.47   6.450%   $120.7888   $120.79   $120.80   $120.80  
  Purchase #7 $169.65   8.375%   $183.8582   $183.86   $183.85   $183.90  
  7 purchase totals = $872.71       $941.7447   $941.76   $941.80   $941.80