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 $170.81   3.150%   $176.1905   $176.19   $176.20   $176.20  
  Purchase #2 $73.73   5.344%   $77.6701   $77.67   $77.65   $77.70  
  Purchase #3 $242.71   10.772%   $268.8547   $268.85   $268.85   $268.90  
  Purchase #4 $203.41   6.867%   $217.3782   $217.38   $217.40   $217.40  
  Purchase #5 $245.58   12.365%   $275.946   $275.95   $275.95   $275.90  
  Purchase #6 $153.33   5.738%   $162.1281   $162.13   $162.15   $162.10  
  Purchase #7 $236.70   11.806%   $264.6448   $264.64   $264.65   $264.60  
  7 purchase totals = $1,326.27       $1,442.8124   $1,442.81   $1,442.85   $1,442.80