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 $58.45   3.505%   $60.4987   $60.50   $60.50   $60.50  
  Purchase #2 $138.81   9.140%   $151.4972   $151.50   $151.50   $151.50  
  Purchase #3 $171.34   7.416%   $184.0466   $184.05   $184.05   $184.00  
  Purchase #4 $209.43   11.163%   $232.8087   $232.81   $232.80   $232.80  
  Purchase #5 $131.48   5.416%   $138.601   $138.60   $138.60   $138.60  
  Purchase #6 $70.26   4.561%   $73.4646   $73.46   $73.45   $73.50  
  Purchase #7 $192.89   11.381%   $214.8428   $214.84   $214.85   $214.80  
  7 purchase totals = $972.66       $1,055.7596   $1,055.76   $1,055.75   $1,055.70