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	$26.64	7.523%	$28.6441	$28.64	$28.65	$28.60
Purchase #2	$187.27	11.606%	$209.0046	$209.00	$209.00	$209.00
Purchase #3	$229.64	5.843%	$243.0579	$243.06	$243.05	$243.10
Purchase #4	$123.77	3.322%	$127.8816	$127.88	$127.90	$127.90
Purchase #5	$65.25	11.496%	$72.7511	$72.75	$72.75	$72.80
Purchase #6	$11.54	5.551%	$12.1806	$12.18	$12.20	$12.20
Purchase #7	$49.93	6.491%	$53.171	$53.17	$53.15	$53.20
7 purchase totals =	$694.04		$746.6909	$746.68	$746.70	$746.80