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 $89.75   5.512%   $94.697   $94.70   $94.70   $94.70  
  Purchase #2 $235.63   4.560%   $246.3747   $246.37   $246.35   $246.40  
  Purchase #3 $123.55   8.698%   $134.2964   $134.30   $134.30   $134.30  
  Purchase #4 $204.27   10.251%   $225.2097   $225.21   $225.20   $225.20  
  Purchase #5 $146.35   11.712%   $163.4905   $163.49   $163.50   $163.50  
  Purchase #6 $90.52   11.734%   $101.1416   $101.14   $101.15   $101.10  
  Purchase #7 $235.26   10.739%   $260.5246   $260.52   $260.50   $260.50  
  7 purchase totals = $1,125.33       $1,225.7345   $1,225.73   $1,225.70   $1,225.70