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 $76.84   11.314%   $85.5337   $85.53   $85.55   $85.50  
  Purchase #2 $238.60   5.750%   $252.3195   $252.32   $252.30   $252.30  
  Purchase #3 $210.35   12.211%   $236.0358   $236.04   $236.05   $236.00  
  Purchase #4 $191.61   9.561%   $209.9298   $209.93   $209.95   $209.90  
  Purchase #5 $104.86   5.482%   $110.6084   $110.61   $110.60   $110.60  
  Purchase #6 $106.82   12.296%   $119.9546   $119.95   $119.95   $120.00  
  Purchase #7 $231.38   9.279%   $252.8498   $252.85   $252.85   $252.80  
  7 purchase totals = $1,160.46       $1,267.2316   $1,267.23   $1,267.25   $1,267.10