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 $69.36   9.864%   $76.2017   $76.20   $76.20   $76.20  
  Purchase #2 $169.75   8.472%   $184.1312   $184.13   $184.15   $184.10  
  Purchase #3 $141.96   3.744%   $147.275   $147.28   $147.30   $147.30  
  Purchase #4 $193.92   3.150%   $200.0285   $200.03   $200.05   $200.00  
  Purchase #5 $60.34   13.139%   $68.2681   $68.27   $68.25   $68.30  
  Purchase #6 $145.36   6.826%   $155.2823   $155.28   $155.30   $155.30  
  Purchase #7 $113.93   8.720%   $123.8647   $123.86   $123.85   $123.90  
  7 purchase totals = $894.62       $955.0515   $955.05   $955.10   $955.10