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 $187.41   4.543%   $195.924   $195.92   $195.90   $195.90  
  Purchase #2 $24.59   8.117%   $26.586   $26.59   $26.60   $26.60  
  Purchase #3 $221.30   10.507%   $244.552   $244.55   $244.55   $244.60  
  Purchase #4 $219.78   9.355%   $240.3404   $240.34   $240.35   $240.30  
  Purchase #5 $112.58   5.724%   $119.0241   $119.02   $119.00   $119.00  
  Purchase #6 $159.50   10.753%   $176.651   $176.65   $176.65   $176.70  
  Purchase #7 $58.71   11.677%   $65.5656   $65.57   $65.55   $65.60  
  7 purchase totals = $983.87       $1,068.6431   $1,068.64   $1,068.60   $1,068.70