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 $182.50   6.608%   $194.5596   $194.56   $194.55   $194.60  
  Purchase #2 $41.46   11.619%   $46.2772   $46.28   $46.30   $46.30  
  Purchase #3 $135.27   13.591%   $153.6545   $153.65   $153.65   $153.70  
  Purchase #4 $119.77   4.153%   $124.744   $124.74   $124.75   $124.70  
  Purchase #5 $169.82   3.619%   $175.9658   $175.97   $175.95   $176.00  
  Purchase #6 $244.25   5.320%   $257.2441   $257.24   $257.25   $257.20  
  Purchase #7 $180.53   7.382%   $193.8567   $193.86   $193.85   $193.90  
  7 purchase totals = $1,073.60       $1,146.3019   $1,146.30   $1,146.30   $1,146.40