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 $62.50   13.534%   $70.9588   $70.96   $70.95   $71.00  
  Purchase #2 $183.81   6.398%   $195.5702   $195.57   $195.55   $195.60  
  Purchase #3 $99.55   12.548%   $112.0415   $112.04   $112.05   $112.00  
  Purchase #4 $247.95   11.498%   $276.4593   $276.46   $276.45   $276.50  
  Purchase #5 $170.79   12.155%   $191.5495   $191.55   $191.55   $191.50  
  Purchase #6 $118.54   9.132%   $129.3651   $129.37   $129.35   $129.40  
  Purchase #7 $202.98   11.338%   $225.9939   $225.99   $226.00   $226.00  
  7 purchase totals = $1,086.12       $1,201.9383   $1,201.94   $1,201.90   $1,202.00