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 $148.27   11.405%   $165.1802   $165.18   $165.20   $165.20  
  Purchase #2 $245.88   6.197%   $261.1172   $261.12   $261.10   $261.10  
  Purchase #3 $42.66   9.214%   $46.5907   $46.59   $46.60   $46.60  
  Purchase #4 $234.74   5.415%   $247.4512   $247.45   $247.45   $247.50  
  Purchase #5 $125.48   6.492%   $133.6262   $133.63   $133.65   $133.60  
  Purchase #6 $100.84   7.500%   $108.403   $108.40   $108.40   $108.40  
  Purchase #7 $59.47   6.272%   $63.2   $63.20   $63.20   $63.20  
  7 purchase totals = $957.34       $1,025.5685   $1,025.57   $1,025.60   $1,025.60