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 $131.93   9.858%   $144.9357   $144.94   $144.95   $144.90  
  Purchase #2 $182.84   6.523%   $194.7667   $194.77   $194.75   $194.80  
  Purchase #3 $86.95   9.747%   $95.425   $95.43   $95.45   $95.40  
  Purchase #4 $199.49   6.504%   $212.4648   $212.46   $212.45   $212.50  
  Purchase #5 $132.31   12.281%   $148.559   $148.56   $148.55   $148.60  
  Purchase #6 $176.48   9.323%   $192.9332   $192.93   $192.95   $192.90  
  Purchase #7 $70.51   4.287%   $73.5328   $73.53   $73.55   $73.50  
  7 purchase totals = $980.51       $1,062.6172   $1,062.62   $1,062.65   $1,062.60