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 $206.42   9.507%   $226.0443   $226.04   $226.05   $226.00  
  Purchase #2 $214.93   12.254%   $241.2675   $241.27   $241.25   $241.30  
  Purchase #3 $112.27   12.428%   $126.2229   $126.22   $126.20   $126.20  
  Purchase #4 $54.85   7.609%   $59.0235   $59.02   $59.00   $59.00  
  Purchase #5 $192.62   11.390%   $214.5594   $214.56   $214.55   $214.60  
  Purchase #6 $106.29   3.150%   $109.6381   $109.64   $109.65   $109.60  
  Purchase #7 $214.40   7.244%   $229.9311   $229.93   $229.95   $229.90  
  7 purchase totals = $1,101.78       $1,206.6868   $1,206.68   $1,206.65   $1,206.60