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 $85.92   11.754%   $96.019   $96.02   $96.00   $96.00  
  Purchase #2 $73.73   12.219%   $82.7391   $82.74   $82.75   $82.70  
  Purchase #3 $59.60   8.385%   $64.5975   $64.60   $64.60   $64.60  
  Purchase #4 $13.50   4.738%   $14.1396   $14.14   $14.15   $14.10  
  Purchase #5 $102.34   8.182%   $110.7135   $110.71   $110.70   $110.70  
  Purchase #6 $192.88   10.263%   $212.6753   $212.68   $212.70   $212.70  
  Purchase #7 $204.80   3.741%   $212.4616   $212.46   $212.45   $212.50  
  7 purchase totals = $732.77       $793.3456   $793.35   $793.35   $793.30