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 $84.28   12.728%   $95.0072   $95.01   $95.00   $95.00  
  Purchase #2 $247.84   10.489%   $273.8359   $273.84   $273.85   $273.80  
  Purchase #3 $43.30   13.326%   $49.0702   $49.07   $49.05   $49.10  
  Purchase #4 $89.56   5.463%   $94.4527   $94.45   $94.45   $94.50  
  Purchase #5 $248.59   7.868%   $268.1491   $268.15   $268.15   $268.10  
  Purchase #6 $128.27   4.391%   $133.9023   $133.90   $133.90   $133.90  
  Purchase #7 $27.44   13.667%   $31.1902   $31.19   $31.20   $31.20  
  7 purchase totals = $869.28       $945.6076   $945.61   $945.60   $945.60