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 $187.89   10.146%   $206.9533   $206.95   $206.95   $207.00  
  Purchase #2 $129.52   9.205%   $141.4423   $141.44   $141.45   $141.40  
  Purchase #3 $226.97   4.230%   $236.5708   $236.57   $236.55   $236.60  
  Purchase #4 $41.45   10.343%   $45.7372   $45.74   $45.75   $45.70  
  Purchase #5 $141.66   12.736%   $159.7018   $159.70   $159.70   $159.70  
  Purchase #6 $185.44   8.601%   $201.3897   $201.39   $201.40   $201.40  
  Purchase #7 $147.64   9.424%   $161.5536   $161.55   $161.55   $161.60  
  7 purchase totals = $1,060.57       $1,153.3487   $1,153.34   $1,153.35   $1,153.40