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 $67.83   5.499%   $71.56   $71.56   $71.55   $71.60  
  Purchase #2 $211.55   6.668%   $225.6562   $225.66   $225.65   $225.70  
  Purchase #3 $23.75   5.378%   $25.0273   $25.03   $25.05   $25.00  
  Purchase #4 $127.28   4.341%   $132.8052   $132.81   $132.80   $132.80  
  Purchase #5 $6.87   3.729%   $7.1262   $7.13   $7.15   $7.10  
  Purchase #6 $158.80   4.203%   $165.4744   $165.47   $165.45   $165.50  
  Purchase #7 $87.97   13.252%   $99.6278   $99.63   $99.65   $99.60  
  7 purchase totals = $684.05       $727.2771   $727.29   $727.30   $727.30