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 $215.94   10.183%   $237.9292   $237.93   $237.95   $237.90  
  Purchase #2 $103.26   7.142%   $110.6348   $110.63   $110.65   $110.60  
  Purchase #3 $158.66   6.354%   $168.7413   $168.74   $168.75   $168.70  
  Purchase #4 $12.32   9.310%   $13.467   $13.47   $13.45   $13.50  
  Purchase #5 $204.76   7.125%   $219.3492   $219.35   $219.35   $219.30  
  Purchase #6 $37.44   7.207%   $40.1383   $40.14   $40.15   $40.10  
  Purchase #7 $238.53   7.486%   $256.3864   $256.39   $256.40   $256.40  
  7 purchase totals = $970.91       $1,046.6462   $1,046.65   $1,046.70   $1,046.50