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 $87.25   7.205%   $93.5364   $93.54   $93.55   $93.50  
  Purchase #2 $243.58   5.420%   $256.782   $256.78   $256.80   $256.80  
  Purchase #3 $209.98   8.848%   $228.559   $228.56   $228.55   $228.60  
  Purchase #4 $54.76   5.126%   $57.567   $57.57   $57.55   $57.60  
  Purchase #5 $154.62   13.668%   $175.7535   $175.75   $175.75   $175.80  
  Purchase #6 $168.69   9.755%   $185.1457   $185.15   $185.15   $185.10  
  Purchase #7 $101.58   6.544%   $108.2274   $108.23   $108.25   $108.20  
  7 purchase totals = $1,020.46       $1,105.5710   $1,105.58   $1,105.60   $1,105.60