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 $87.49   9.554%   $95.8488   $95.85   $95.85   $95.80  
  Purchase #2 $201.27   8.707%   $218.7946   $218.79   $218.80   $218.80  
  Purchase #3 $195.49   10.466%   $215.95   $215.95   $215.95   $216.00  
  Purchase #4 $162.76   11.398%   $181.3114   $181.31   $181.30   $181.30  
  Purchase #5 $233.36   4.521%   $243.9102   $243.91   $243.90   $243.90  
  Purchase #6 $183.85   10.388%   $202.9483   $202.95   $202.95   $202.90  
  Purchase #7 $71.96   5.538%   $75.9451   $75.95   $75.95   $75.90  
  7 purchase totals = $1,136.18       $1,234.7084   $1,234.71   $1,234.70   $1,234.60