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 $196.36   7.305%   $210.7041   $210.70   $210.70   $210.70  
  Purchase #2 $194.76   5.757%   $205.9723   $205.97   $205.95   $206.00  
  Purchase #3 $59.89   12.691%   $67.4906   $67.49   $67.50   $67.50  
  Purchase #4 $105.57   9.861%   $115.9803   $115.98   $116.00   $116.00  
  Purchase #5 $62.46   6.362%   $66.4337   $66.43   $66.45   $66.40  
  Purchase #6 $89.79   7.726%   $96.7272   $96.73   $96.75   $96.70  
  Purchase #7 $235.35   3.144%   $242.7494   $242.75   $242.75   $242.70  
  7 purchase totals = $944.18       $1,006.0576   $1,006.05   $1,006.10   $1,006.00