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	$50.26	4.662%	$52.6031	$52.60	$52.60	$52.60
Purchase #2	$242.33	4.818%	$254.0055	$254.01	$254.00	$254.00
Purchase #3	$247.27	13.785%	$281.3562	$281.36	$281.35	$281.40
Purchase #4	$95.97	6.345%	$102.0593	$102.06	$102.05	$102.10
Purchase #5	$122.25	4.499%	$127.75	$127.75	$127.75	$127.80
Purchase #6	$205.71	5.154%	$216.3123	$216.31	$216.30	$216.30
Purchase #7	$241.87	13.530%	$274.595	$274.60	$274.60	$274.60
7 purchase totals =	$1,205.66		$1,308.6814	$1,308.69	$1,308.65	$1,308.80