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 $197.25   4.442%   $206.0118   $206.01   $206.00   $206.00  
  Purchase #2 $250.47   7.343%   $268.862   $268.86   $268.85   $268.90  
  Purchase #3 $88.55   9.428%   $96.8985   $96.90   $96.90   $96.90  
  Purchase #4 $229.55   5.115%   $241.2915   $241.29   $241.30   $241.30  
  Purchase #5 $109.76   7.698%   $118.2093   $118.21   $118.20   $118.20  
  Purchase #6 $189.55   7.229%   $203.2526   $203.25   $203.25   $203.30  
  Purchase #7 $7.73   10.509%   $8.5423   $8.54   $8.55   $8.50  
  7 purchase totals = $1,072.86       $1,143.0680   $1,143.06   $1,143.05   $1,143.10