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 $82.88   6.248%   $88.0583   $88.06   $88.05   $88.10  
  Purchase #2 $149.95   4.266%   $156.3469   $156.35   $156.35   $156.30  
  Purchase #3 $101.91   12.152%   $114.2941   $114.29   $114.30   $114.30  
  Purchase #4 $38.25   9.114%   $41.7361   $41.74   $41.75   $41.70  
  Purchase #5 $178.62   6.551%   $190.3214   $190.32   $190.30   $190.30  
  Purchase #6 $222.43   10.258%   $245.2469   $245.25   $245.25   $245.20  
  Purchase #7 $197.30   10.540%   $218.0954   $218.10   $218.10   $218.10  
  7 purchase totals = $971.34       $1,054.0991   $1,054.11   $1,054.10   $1,054.00