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 $213.31   5.330%   $224.6794   $224.68   $224.70   $224.70  
  Purchase #2 $63.61   7.375%   $68.3012   $68.30   $68.30   $68.30  
  Purchase #3 $189.72   11.503%   $211.5435   $211.54   $211.55   $211.50  
  Purchase #4 $185.73   4.569%   $194.216   $194.22   $194.20   $194.20  
  Purchase #5 $54.70   10.840%   $60.6295   $60.63   $60.65   $60.60  
  Purchase #6 $159.77   4.532%   $167.0108   $167.01   $167.00   $167.00  
  Purchase #7 $25.87   3.869%   $26.8709   $26.87   $26.85   $26.90  
  7 purchase totals = $892.71       $953.2513   $953.25   $953.25   $953.20