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 $84.59   11.304%   $94.1521   $94.15   $94.15   $94.20  
  Purchase #2 $130.97   9.390%   $143.2681   $143.27   $143.25   $143.30  
  Purchase #3 $190.39   3.111%   $196.313   $196.31   $196.30   $196.30  
  Purchase #4 $227.92   8.203%   $246.6163   $246.62   $246.60   $246.60  
  Purchase #5 $237.29   4.127%   $247.083   $247.08   $247.10   $247.10  
  Purchase #6 $67.33   11.562%   $75.1147   $75.11   $75.10   $75.10  
  Purchase #7 $247.84   5.459%   $261.3696   $261.37   $261.35   $261.40  
  7 purchase totals = $1,186.33       $1,263.9168   $1,263.91   $1,263.85   $1,264.00