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 $62.68   7.454%   $67.3522   $67.35   $67.35   $67.40  
  Purchase #2 $157.51   10.150%   $173.4973   $173.50   $173.50   $173.50  
  Purchase #3 $118.49   6.538%   $126.2369   $126.24   $126.25   $126.20  
  Purchase #4 $133.30   10.635%   $147.4765   $147.48   $147.50   $147.50  
  Purchase #5 $165.77   10.456%   $183.1029   $183.10   $183.10   $183.10  
  Purchase #6 $175.96   4.864%   $184.5187   $184.52   $184.50   $184.50  
  Purchase #7 $69.41   9.166%   $75.7721   $75.77   $75.75   $75.80  
  7 purchase totals = $883.12       $957.9566   $957.96   $957.95   $958.00