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 $57.73   7.295%   $61.9414   $61.94   $61.95   $61.90  
  Purchase #2 $195.84   7.411%   $210.3537   $210.35   $210.35   $210.40  
  Purchase #3 $231.28   7.137%   $247.7865   $247.79   $247.80   $247.80  
  Purchase #4 $219.78   3.676%   $227.8591   $227.86   $227.85   $227.90  
  Purchase #5 $193.68   4.450%   $202.2988   $202.30   $202.30   $202.30  
  Purchase #6 $155.39   8.340%   $168.3495   $168.35   $168.35   $168.30  
  Purchase #7 $164.99   11.195%   $183.4606   $183.46   $183.45   $183.50  
  7 purchase totals = $1,218.69       $1,302.0496   $1,302.05   $1,302.05   $1,302.10