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 $190.62   5.323%   $200.7667   $200.77   $200.75   $200.80  
  Purchase #2 $50.41   12.403%   $56.6624   $56.66   $56.65   $56.70  
  Purchase #3 $132.66   3.749%   $137.6334   $137.63   $137.65   $137.60  
  Purchase #4 $65.63   5.627%   $69.323   $69.32   $69.30   $69.30  
  Purchase #5 $238.71   10.362%   $263.4451   $263.45   $263.45   $263.40  
  Purchase #6 $160.29   4.389%   $167.3251   $167.33   $167.35   $167.30  
  Purchase #7 $198.80   3.639%   $206.0343   $206.03   $206.05   $206.00  
  7 purchase totals = $1,037.12       $1,101.1900   $1,101.19   $1,101.20   $1,101.10