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	$201.60	3.459%	$208.5733	$208.57	$208.55	$208.60
Purchase #2	$49.82	10.410%	$55.0063	$55.01	$55.00	$55.00
Purchase #3	$211.31	7.829%	$227.8535	$227.85	$227.85	$227.90
Purchase #4	$221.83	7.322%	$238.0724	$238.07	$238.05	$238.10
Purchase #5	$108.78	4.372%	$113.5359	$113.54	$113.55	$113.50
Purchase #6	$69.58	4.705%	$72.8537	$72.85	$72.85	$72.90
Purchase #7	$165.87	5.729%	$175.3727	$175.37	$175.35	$175.40
7 purchase totals =	$1,028.79		$1,091.2678	$1,091.26	$1,091.20	$1,091.40