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 $84.59   12.568%   $95.2213   $95.22   $95.20   $95.20  
  Purchase #2 $163.35   5.417%   $172.1987   $172.20   $172.20   $172.20  
  Purchase #3 $197.77   3.412%   $204.5179   $204.52   $204.50   $204.50  
  Purchase #4 $11.44   10.775%   $12.6727   $12.67   $12.65   $12.70  
  Purchase #5 $174.36   13.160%   $197.3058   $197.31   $197.30   $197.30  
  Purchase #6 $194.75   6.528%   $207.4633   $207.46   $207.45   $207.50  
  Purchase #7 $194.48   10.773%   $215.4313   $215.43   $215.45   $215.40  
  7 purchase totals = $1,020.74       $1,104.8110   $1,104.81   $1,104.75   $1,104.80