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 $212.63   5.683%   $224.7138   $224.71   $224.70   $224.70  
  Purchase #2 $227.68   8.129%   $246.1881   $246.19   $246.20   $246.20  
  Purchase #3 $141.53   9.852%   $155.4735   $155.47   $155.45   $155.50  
  Purchase #4 $96.68   12.393%   $108.6616   $108.66   $108.65   $108.70  
  Purchase #5 $48.53   5.751%   $51.321   $51.32   $51.30   $51.30  
  Purchase #6 $224.58   7.629%   $241.7132   $241.71   $241.70   $241.70  
  Purchase #7 $100.48   7.179%   $107.6935   $107.69   $107.70   $107.70  
  7 purchase totals = $1,052.11       $1,135.7647   $1,135.75   $1,135.70   $1,135.80