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 $43.75   10.264%   $48.2405   $48.24   $48.25   $48.20  
  Purchase #2 $84.90   13.668%   $96.5041   $96.50   $96.50   $96.50  
  Purchase #3 $184.97   5.240%   $194.6624   $194.66   $194.65   $194.70  
  Purchase #4 $239.86   12.249%   $269.2405   $269.24   $269.25   $269.20  
  Purchase #5 $198.61   11.707%   $221.8613   $221.86   $221.85   $221.90  
  Purchase #6 $235.76   8.706%   $256.2853   $256.29   $256.30   $256.30  
  Purchase #7 $53.46   6.850%   $57.122   $57.12   $57.10   $57.10  
  7 purchase totals = $1,041.31       $1,143.9161   $1,143.91   $1,143.90   $1,143.90