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 $116.60   7.411%   $125.2412   $125.24   $125.25   $125.20  
  Purchase #2 $203.68   7.513%   $218.9825   $218.98   $219.00   $219.00  
  Purchase #3 $243.38   6.165%   $258.3844   $258.38   $258.40   $258.40  
  Purchase #4 $146.80   4.576%   $153.5176   $153.52   $153.50   $153.50  
  Purchase #5 $181.73   11.645%   $202.8925   $202.89   $202.90   $202.90  
  Purchase #6 $165.78   6.600%   $176.7215   $176.72   $176.70   $176.70  
  Purchase #7 $13.71   12.448%   $15.4166   $15.42   $15.40   $15.40  
  7 purchase totals = $1,071.68       $1,151.1563   $1,151.15   $1,151.15   $1,151.10