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 $59.53   5.205%   $62.6285   $62.63   $62.65   $62.60  
  Purchase #2 $46.40   9.721%   $50.9105   $50.91   $50.90   $50.90  
  Purchase #3 $201.28   4.272%   $209.8787   $209.88   $209.90   $209.90  
  Purchase #4 $169.86   11.731%   $189.7863   $189.79   $189.80   $189.80  
  Purchase #5 $185.70   9.167%   $202.7231   $202.72   $202.70   $202.70  
  Purchase #6 $239.87   5.527%   $253.1276   $253.13   $253.15   $253.10  
  Purchase #7 $173.62   8.825%   $188.942   $188.94   $188.95   $188.90  
  7 purchase totals = $1,076.26       $1,157.9967   $1,158.00   $1,158.05   $1,157.90