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 $58.65   4.502%   $61.2904   $61.29   $61.30   $61.30  
  Purchase #2 $59.30   8.128%   $64.1199   $64.12   $64.10   $64.10  
  Purchase #3 $213.58   7.214%   $228.9877   $228.99   $229.00   $229.00  
  Purchase #4 $231.25   4.823%   $242.4032   $242.40   $242.40   $242.40  
  Purchase #5 $162.86   4.626%   $170.3939   $170.39   $170.40   $170.40  
  Purchase #6 $233.85   12.766%   $263.7033   $263.70   $263.70   $263.70  
  Purchase #7 $216.91   11.230%   $241.269   $241.27   $241.25   $241.30  
  7 purchase totals = $1,176.40       $1,272.1674   $1,272.16   $1,272.15   $1,272.20