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	$178.72	8.501%	$193.913	$193.91	$193.90	$193.90
Purchase #2	$107.50	3.715%	$111.4936	$111.49	$111.50	$111.50
Purchase #3	$134.83	3.373%	$139.3778	$139.38	$139.40	$139.40
Purchase #4	$24.74	11.444%	$27.5712	$27.57	$27.55	$27.60
Purchase #5	$55.90	7.508%	$60.097	$60.10	$60.10	$60.10
Purchase #6	$87.96	3.501%	$91.0395	$91.04	$91.05	$91.00
Purchase #7	$93.81	12.461%	$105.4997	$105.50	$105.50	$105.50
7 purchase totals =	$683.46		$728.9918	$728.99	$729.00	$729.00