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	$95.91	9.228%	$104.7606	$104.76	$104.75	$104.80
Purchase #2	$33.40	5.595%	$35.2687	$35.27	$35.25	$35.30
Purchase #3	$35.89	11.162%	$39.896	$39.90	$39.90	$39.90
Purchase #4	$50.94	12.394%	$57.2535	$57.25	$57.25	$57.30
Purchase #5	$49.88	8.547%	$54.1432	$54.14	$54.15	$54.10
Purchase #6	$228.48	3.518%	$236.5179	$236.52	$236.50	$236.50
Purchase #7	$12.44	8.192%	$13.4591	$13.46	$13.45	$13.50
7 purchase totals =	$506.94		$541.2990	$541.30	$541.25	$541.40