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 $43.30   11.494%   $48.2769   $48.28   $48.30   $48.30  
  Purchase #2 $200.31   6.690%   $213.7107   $213.71   $213.70   $213.70  
  Purchase #3 $213.26   8.799%   $232.0247   $232.02   $232.00   $232.00  
  Purchase #4 $64.51   5.305%   $67.9323   $67.93   $67.95   $67.90  
  Purchase #5 $154.50   3.178%   $159.41   $159.41   $159.40   $159.40  
  Purchase #6 $248.90   8.428%   $269.8773   $269.88   $269.90   $269.90  
  Purchase #7 $165.82   11.440%   $184.7898   $184.79   $184.80   $184.80  
  7 purchase totals = $1,090.60       $1,176.0217   $1,176.02   $1,176.05   $1,176.00