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 $195.63   12.278%   $219.6495   $219.65   $219.65   $219.60  
  Purchase #2 $220.97   13.459%   $250.7104   $250.71   $250.70   $250.70  
  Purchase #3 $203.33   6.593%   $216.7355   $216.74   $216.75   $216.70  
  Purchase #4 $33.82   13.498%   $38.385   $38.39   $38.40   $38.40  
  Purchase #5 $92.82   3.353%   $95.9323   $95.93   $95.95   $95.90  
  Purchase #6 $133.68   9.309%   $146.1243   $146.12   $146.10   $146.10  
  Purchase #7 $178.94   11.777%   $200.0138   $200.01   $200.00   $200.00  
  7 purchase totals = $1,059.19       $1,167.5508   $1,167.55   $1,167.55   $1,167.40