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 $243.34   7.676%   $262.0188   $262.02   $262.00   $262.00  
  Purchase #2 $213.80   5.615%   $225.8049   $225.80   $225.80   $225.80  
  Purchase #3 $88.73   5.625%   $93.7211   $93.72   $93.70   $93.70  
  Purchase #4 $145.71   5.217%   $153.3117   $153.31   $153.30   $153.30  
  Purchase #5 $158.44   11.501%   $176.6622   $176.66   $176.65   $176.70  
  Purchase #6 $232.95   6.363%   $247.7726   $247.77   $247.75   $247.80  
  Purchase #7 $57.87   5.756%   $61.201   $61.20   $61.20   $61.20  
  7 purchase totals = $1,140.84       $1,220.4923   $1,220.48   $1,220.40   $1,220.50