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	$181.91	7.461%	$195.4823	$195.48	$195.50	$195.50
Purchase #2	$105.85	3.401%	$109.45	$109.45	$109.45	$109.50
Purchase #3	$101.83	5.290%	$107.2168	$107.22	$107.20	$107.20
Purchase #4	$230.99	13.774%	$262.8066	$262.81	$262.80	$262.80
Purchase #5	$59.77	4.207%	$62.2845	$62.28	$62.30	$62.30
Purchase #6	$35.43	13.333%	$40.1539	$40.15	$40.15	$40.20
Purchase #7	$175.85	11.159%	$195.4731	$195.47	$195.45	$195.50
7 purchase totals =	$891.63		$972.8672	$972.86	$972.85	$973.00