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 $244.33   7.694%   $263.1288   $263.13   $263.15   $263.10  
  Purchase #2 $64.30   10.710%   $71.1865   $71.19   $71.20   $71.20  
  Purchase #3 $93.45   8.681%   $101.5624   $101.56   $101.55   $101.60  
  Purchase #4 $147.93   12.557%   $166.5056   $166.51   $166.50   $166.50  
  Purchase #5 $66.40   13.192%   $75.1595   $75.16   $75.15   $75.20  
  Purchase #6 $152.95   10.193%   $168.5402   $168.54   $168.55   $168.50  
  Purchase #7 $187.96   9.777%   $206.3368   $206.34   $206.35   $206.30  
  7 purchase totals = $957.32       $1,052.4198   $1,052.43   $1,052.45   $1,052.40