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 $91.90   4.414%   $95.9565   $95.96   $95.95   $96.00  
  Purchase #2 $195.36   6.771%   $208.5878   $208.59   $208.60   $208.60  
  Purchase #3 $25.38   7.777%   $27.3538   $27.35   $27.35   $27.40  
  Purchase #4 $236.74   12.410%   $266.1194   $266.12   $266.10   $266.10  
  Purchase #5 $46.42   10.443%   $51.2676   $51.27   $51.25   $51.30  
  Purchase #6 $205.88   6.686%   $219.6451   $219.65   $219.65   $219.60  
  Purchase #7 $232.44   9.628%   $254.8193   $254.82   $254.80   $254.80  
  7 purchase totals = $1,034.12       $1,123.7495   $1,123.76   $1,123.70   $1,123.80