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 $46.27   5.173%   $48.6635   $48.66   $48.65   $48.70  
  Purchase #2 $229.91   9.556%   $251.8802   $251.88   $251.90   $251.90  
  Purchase #3 $59.28   6.236%   $62.9767   $62.98   $63.00   $63.00  
  Purchase #4 $86.89   9.554%   $95.1915   $95.19   $95.20   $95.20  
  Purchase #5 $241.70   5.775%   $255.6582   $255.66   $255.65   $255.70  
  Purchase #6 $100.31   7.585%   $107.9185   $107.92   $107.90   $107.90  
  Purchase #7 $150.30   13.461%   $170.5319   $170.53   $170.55   $170.50  
  7 purchase totals = $914.66       $992.8205   $992.82   $992.85   $992.90