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 $22.98   5.259%   $24.1885   $24.19   $24.20   $24.20  
  Purchase #2 $248.73   9.662%   $272.7623   $272.76   $272.75   $272.80  
  Purchase #3 $150.43   12.241%   $168.8441   $168.84   $168.85   $168.80  
  Purchase #4 $242.83   11.151%   $269.908   $269.91   $269.90   $269.90  
  Purchase #5 $54.34   12.516%   $61.1412   $61.14   $61.15   $61.10  
  Purchase #6 $195.92   8.786%   $213.1335   $213.13   $213.15   $213.10  
  Purchase #7 $91.52   7.471%   $98.3575   $98.36   $98.35   $98.40  
  7 purchase totals = $1,006.75       $1,108.3351   $1,108.33   $1,108.35   $1,108.30