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 $119.65   5.785%   $126.5718   $126.57   $126.55   $126.60  
  Purchase #2 $169.93   10.375%   $187.5602   $187.56   $187.55   $187.60  
  Purchase #3 $227.43   3.499%   $235.3878   $235.39   $235.40   $235.40  
  Purchase #4 $185.62   8.281%   $200.9912   $200.99   $201.00   $201.00  
  Purchase #5 $233.82   6.164%   $248.2327   $248.23   $248.25   $248.20  
  Purchase #6 $26.33   11.136%   $29.2621   $29.26   $29.25   $29.30  
  Purchase #7 $181.64   13.598%   $206.3394   $206.34   $206.35   $206.30  
  7 purchase totals = $1,144.42       $1,234.3452   $1,234.34   $1,234.35   $1,234.40