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	$172.97	13.174%	$195.7571	$195.76	$195.75	$195.80
Purchase #2	$136.93	8.652%	$148.7772	$148.78	$148.80	$148.80
Purchase #3	$82.93	7.413%	$89.0776	$89.08	$89.10	$89.10
Purchase #4	$84.99	4.460%	$88.7806	$88.78	$88.80	$88.80
Purchase #5	$117.60	8.579%	$127.6889	$127.69	$127.70	$127.70
Purchase #6	$188.81	5.211%	$198.6489	$198.65	$198.65	$198.60
Purchase #7	$197.75	12.810%	$223.0818	$223.08	$223.10	$223.10
7 purchase totals =	$981.98		$1,071.8121	$1,071.82	$1,071.90	$1,071.90