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 $86.82   7.419%   $93.2612   $93.26   $93.25   $93.30  
  Purchase #2 $204.59   9.679%   $224.3923   $224.39   $224.40   $224.40  
  Purchase #3 $223.39   4.195%   $232.7612   $232.76   $232.75   $232.80  
  Purchase #4 $23.70   8.325%   $25.673   $25.67   $25.65   $25.70  
  Purchase #5 $232.47   6.246%   $246.9901   $246.99   $247.00   $247.00  
  Purchase #6 $222.91   10.572%   $246.476   $246.48   $246.50   $246.50  
  Purchase #7 $132.28   9.185%   $144.4299   $144.43   $144.45   $144.40  
  7 purchase totals = $1,126.16       $1,213.9837   $1,213.98   $1,214.00   $1,214.10