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 $218.54   3.829%   $226.9079   $226.91   $226.90   $226.90  
  Purchase #2 $210.82   11.453%   $234.9652   $234.97   $234.95   $235.00  
  Purchase #3 $43.74   9.110%   $47.7247   $47.72   $47.70   $47.70  
  Purchase #4 $42.58   5.742%   $45.0249   $45.02   $45.00   $45.00  
  Purchase #5 $132.78   12.610%   $149.5236   $149.52   $149.50   $149.50  
  Purchase #6 $168.49   11.554%   $187.9573   $187.96   $187.95   $188.00  
  Purchase #7 $200.76   8.722%   $218.2703   $218.27   $218.25   $218.30  
  7 purchase totals = $1,017.71       $1,110.3739   $1,110.37   $1,110.25   $1,110.40