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 $60.42   5.692%   $63.8591   $63.86   $63.85   $63.90  
  Purchase #2 $219.31   5.391%   $231.133   $231.13   $231.15   $231.10  
  Purchase #3 $204.34   4.120%   $212.7588   $212.76   $212.75   $212.80  
  Purchase #4 $235.38   8.545%   $255.4932   $255.49   $255.50   $255.50  
  Purchase #5 $117.73   11.623%   $131.4138   $131.41   $131.40   $131.40  
  Purchase #6 $5.95   7.816%   $6.4151   $6.42   $6.40   $6.40  
  Purchase #7 $36.52   10.484%   $40.3488   $40.35   $40.35   $40.30  
  7 purchase totals = $879.65       $941.4218   $941.42   $941.40   $941.40