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	$29.29	7.315%	$31.4326	$31.43	$31.45	$31.40
Purchase #2	$9.49	12.811%	$10.7058	$10.71	$10.70	$10.70
Purchase #3	$145.87	7.272%	$156.4777	$156.48	$156.50	$156.50
Purchase #4	$152.27	13.425%	$172.7122	$172.71	$172.70	$172.70
Purchase #5	$198.82	12.508%	$223.6884	$223.69	$223.70	$223.70
Purchase #6	$233.55	7.110%	$250.1554	$250.16	$250.15	$250.20
Purchase #7	$212.61	7.752%	$229.0915	$229.09	$229.10	$229.10
7 purchase totals =	$981.90		$1,074.2636	$1,074.27	$1,074.30	$1,074.30