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 $67.60   10.872%   $74.9495   $74.95   $74.95   $74.90  
  Purchase #2 $83.93   9.616%   $92.0007   $92.00   $92.00   $92.00  
  Purchase #3 $110.99   6.383%   $118.0745   $118.07   $118.05   $118.10  
  Purchase #4 $194.82   5.640%   $205.8078   $205.81   $205.80   $205.80  
  Purchase #5 $109.76   10.446%   $121.2255   $121.23   $121.25   $121.20  
  Purchase #6 $206.81   9.352%   $226.1509   $226.15   $226.15   $226.20  
  Purchase #7 $104.82   7.557%   $112.7412   $112.74   $112.75   $112.70  
  7 purchase totals = $878.73       $950.9501   $950.95   $950.95   $950.90