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 $240.96   5.396%   $253.9622   $253.96   $253.95   $254.00  
  Purchase #2 $174.55   11.711%   $194.9916   $194.99   $195.00   $195.00  
  Purchase #3 $217.52   6.219%   $231.0476   $231.05   $231.05   $231.00  
  Purchase #4 $163.82   7.766%   $176.5423   $176.54   $176.55   $176.50  
  Purchase #5 $51.85   4.102%   $53.9769   $53.98   $54.00   $54.00  
  Purchase #6 $65.39   11.128%   $72.6666   $72.67   $72.65   $72.70  
  Purchase #7 $120.35   4.494%   $125.7585   $125.76   $125.75   $125.80  
  7 purchase totals = $1,034.44       $1,108.9457   $1,108.95   $1,108.95   $1,109.00