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 $54.49   7.817%   $58.7495   $58.75   $58.75   $58.70  
  Purchase #2 $216.92   13.758%   $246.7639   $246.76   $246.75   $246.80  
  Purchase #3 $216.70   11.238%   $241.0527   $241.05   $241.05   $241.10  
  Purchase #4 $111.46   8.312%   $120.7246   $120.72   $120.70   $120.70  
  Purchase #5 $211.82   8.234%   $229.2613   $229.26   $229.25   $229.30  
  Purchase #6 $192.65   10.109%   $212.125   $212.13   $212.15   $212.10  
  Purchase #7 $200.48   13.648%   $227.8415   $227.84   $227.85   $227.80  
  7 purchase totals = $1,204.52       $1,336.5185   $1,336.51   $1,336.50   $1,336.50