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 $210.64   10.588%   $232.9426   $232.94   $232.95   $232.90  
  Purchase #2 $128.25   3.668%   $132.9542   $132.95   $132.95   $133.00  
  Purchase #3 $230.84   13.663%   $262.3797   $262.38   $262.40   $262.40  
  Purchase #4 $247.45   5.823%   $261.859   $261.86   $261.85   $261.90  
  Purchase #5 $170.31   6.538%   $181.4449   $181.44   $181.45   $181.40  
  Purchase #6 $247.80   11.221%   $275.6056   $275.61   $275.60   $275.60  
  Purchase #7 $106.87   13.347%   $121.1339   $121.13   $121.15   $121.10  
  7 purchase totals = $1,342.16       $1,468.3199   $1,468.31   $1,468.35   $1,468.30