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 $116.50   7.332%   $125.0418   $125.04   $125.05   $125.00  
  Purchase #2 $182.97   6.125%   $194.1769   $194.18   $194.20   $194.20  
  Purchase #3 $19.95   10.344%   $22.0136   $22.01   $22.00   $22.00  
  Purchase #4 $28.73   7.227%   $30.8063   $30.81   $30.80   $30.80  
  Purchase #5 $121.96   9.543%   $133.5986   $133.60   $133.60   $133.60  
  Purchase #6 $116.52   6.420%   $124.0006   $124.00   $124.00   $124.00  
  Purchase #7 $200.43   7.103%   $214.6665   $214.67   $214.65   $214.70  
  7 purchase totals = $787.06       $844.3043   $844.31   $844.30   $844.30