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 $84.44   13.483%   $95.825   $95.83   $95.85   $95.80  
  Purchase #2 $40.62   9.496%   $44.4773   $44.48   $44.50   $44.50  
  Purchase #3 $166.67   11.386%   $185.647   $185.65   $185.65   $185.60  
  Purchase #4 $243.70   10.291%   $268.7792   $268.78   $268.80   $268.80  
  Purchase #5 $235.40   13.797%   $267.8781   $267.88   $267.90   $267.90  
  Purchase #6 $23.83   5.863%   $25.2272   $25.23   $25.25   $25.20  
  Purchase #7 $208.37   5.261%   $219.3323   $219.33   $219.35   $219.30  
  7 purchase totals = $1,003.03       $1,107.1661   $1,107.18   $1,107.30   $1,107.10