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 $117.84   6.558%   $125.5679   $125.57   $125.55   $125.60  
  Purchase #2 $43.75   4.152%   $45.5665   $45.57   $45.55   $45.60  
  Purchase #3 $245.29   5.780%   $259.4678   $259.47   $259.45   $259.50  
  Purchase #4 $177.42   5.180%   $186.6104   $186.61   $186.60   $186.60  
  Purchase #5 $49.83   11.167%   $55.3945   $55.39   $55.40   $55.40  
  Purchase #6 $214.75   13.870%   $244.5358   $244.54   $244.55   $244.50  
  Purchase #7 $247.48   8.680%   $268.9613   $268.96   $268.95   $269.00  
  7 purchase totals = $1,096.36       $1,186.1042   $1,186.11   $1,186.05   $1,186.20