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 $94.96   10.259%   $104.7019   $104.70   $104.70   $104.70  
  Purchase #2 $146.82   5.770%   $155.2915   $155.29   $155.30   $155.30  
  Purchase #3 $55.60   8.848%   $60.5195   $60.52   $60.50   $60.50  
  Purchase #4 $243.63   10.125%   $268.2975   $268.30   $268.30   $268.30  
  Purchase #5 $160.69   9.796%   $176.4312   $176.43   $176.45   $176.40  
  Purchase #6 $73.36   7.604%   $78.9383   $78.94   $78.95   $78.90  
  Purchase #7 $183.57   11.767%   $205.1707   $205.17   $205.15   $205.20  
  7 purchase totals = $958.63       $1,049.3506   $1,049.35   $1,049.35   $1,049.30