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 $88.74   9.317%   $97.0079   $97.01   $97.00   $97.00  
  Purchase #2 $117.78   7.128%   $126.1754   $126.18   $126.20   $126.20  
  Purchase #3 $61.88   6.539%   $65.9263   $65.93   $65.95   $65.90  
  Purchase #4 $248.31   11.374%   $276.5528   $276.55   $276.55   $276.60  
  Purchase #5 $239.43   9.872%   $263.0665   $263.07   $263.05   $263.10  
  Purchase #6 $164.87   7.466%   $177.1792   $177.18   $177.20   $177.20  
  Purchase #7 $91.74   4.375%   $95.7536   $95.75   $95.75   $95.80  
  7 purchase totals = $1,012.75       $1,101.6617   $1,101.67   $1,101.70   $1,101.80