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 $87.25   12.267%   $97.953   $97.95   $97.95   $98.00  
  Purchase #2 $6.96   6.283%   $7.3973   $7.40   $7.40   $7.40  
  Purchase #3 $161.26   9.206%   $176.1056   $176.11   $176.10   $176.10  
  Purchase #4 $91.27   10.306%   $100.6763   $100.68   $100.70   $100.70  
  Purchase #5 $212.48   5.775%   $224.7507   $224.75   $224.75   $224.80  
  Purchase #6 $59.50   13.463%   $67.5105   $67.51   $67.50   $67.50  
  Purchase #7 $233.91   3.829%   $242.8664   $242.87   $242.85   $242.90  
  7 purchase totals = $852.63       $917.2598   $917.27   $917.25   $917.40