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 $93.84   11.484%   $104.6166   $104.62   $104.60   $104.60  
  Purchase #2 $188.79   9.470%   $206.6684   $206.67   $206.65   $206.70  
  Purchase #3 $245.88   6.130%   $260.9524   $260.95   $260.95   $261.00  
  Purchase #4 $216.55   9.818%   $237.8109   $237.81   $237.80   $237.80  
  Purchase #5 $153.36   13.853%   $174.605   $174.61   $174.60   $174.60  
  Purchase #6 $219.39   12.242%   $246.2477   $246.25   $246.25   $246.20  
  Purchase #7 $191.79   11.259%   $213.3836   $213.38   $213.40   $213.40  
  7 purchase totals = $1,309.60       $1,444.2846   $1,444.29   $1,444.25   $1,444.30