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 $53.50   10.663%   $59.2047   $59.20   $59.20   $59.20  
  Purchase #2 $94.26   7.568%   $101.3936   $101.39   $101.40   $101.40  
  Purchase #3 $175.42   13.718%   $199.4841   $199.48   $199.50   $199.50  
  Purchase #4 $243.29   8.530%   $264.0426   $264.04   $264.05   $264.00  
  Purchase #5 $231.31   5.566%   $244.1847   $244.18   $244.20   $244.20  
  Purchase #6 $117.89   6.814%   $125.923   $125.92   $125.90   $125.90  
  Purchase #7 $217.83   13.208%   $246.601   $246.60   $246.60   $246.60  
  7 purchase totals = $1,133.50       $1,240.8337   $1,240.81   $1,240.85   $1,240.80