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 $124.96   7.594%   $134.4495   $134.45   $134.45   $134.40  
  Purchase #2 $208.95   5.735%   $220.9333   $220.93   $220.95   $220.90  
  Purchase #3 $130.74   10.172%   $144.0389   $144.04   $144.05   $144.00  
  Purchase #4 $194.74   4.396%   $203.3008   $203.30   $203.30   $203.30  
  Purchase #5 $211.61   3.677%   $219.3909   $219.39   $219.40   $219.40  
  Purchase #6 $36.44   3.338%   $37.6564   $37.66   $37.65   $37.70  
  Purchase #7 $113.25   3.272%   $116.9555   $116.96   $116.95   $117.00  
  7 purchase totals = $1,020.69       $1,076.7253   $1,076.73   $1,076.75   $1,076.70