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 $87.66   8.751%   $95.3311   $95.33   $95.35   $95.30  
  Purchase #2 $148.65   7.870%   $160.3488   $160.35   $160.35   $160.30  
  Purchase #3 $121.38   10.828%   $134.523   $134.52   $134.50   $134.50  
  Purchase #4 $234.67   4.119%   $244.3361   $244.34   $244.35   $244.30  
  Purchase #5 $41.50   8.178%   $44.8939   $44.89   $44.90   $44.90  
  Purchase #6 $166.97   7.456%   $179.4193   $179.42   $179.40   $179.40  
  Purchase #7 $169.67   5.485%   $178.9764   $178.98   $179.00   $179.00  
  7 purchase totals = $970.50       $1,037.8286   $1,037.83   $1,037.85   $1,037.70