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 $60.58   11.426%   $67.5019   $67.50   $67.50   $67.50  
  Purchase #2 $195.46   12.328%   $219.5563   $219.56   $219.55   $219.60  
  Purchase #3 $46.79   5.132%   $49.1913   $49.19   $49.20   $49.20  
  Purchase #4 $40.51   8.662%   $44.019   $44.02   $44.00   $44.00  
  Purchase #5 $191.41   6.204%   $203.2851   $203.29   $203.30   $203.30  
  Purchase #6 $59.73   5.735%   $63.1555   $63.16   $63.15   $63.20  
  Purchase #7 $200.77   4.165%   $209.1321   $209.13   $209.15   $209.10  
  7 purchase totals = $795.25       $855.8412   $855.85   $855.85   $855.90