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 $180.36   9.572%   $197.6241   $197.62   $197.60   $197.60  
  Purchase #2 $53.74   8.255%   $58.1762   $58.18   $58.20   $58.20  
  Purchase #3 $248.49   6.463%   $264.5499   $264.55   $264.55   $264.50  
  Purchase #4 $120.25   4.585%   $125.7635   $125.76   $125.75   $125.80  
  Purchase #5 $11.61   3.495%   $12.0158   $12.02   $12.00   $12.00  
  Purchase #6 $236.92   7.827%   $255.4637   $255.46   $255.45   $255.50  
  Purchase #7 $90.29   7.600%   $97.152   $97.15   $97.15   $97.20  
  7 purchase totals = $941.66       $1,010.7452   $1,010.74   $1,010.70   $1,010.80