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	$92.50	7.548%	$99.4819	$99.48	$99.50	$99.50
Purchase #2	$122.27	6.442%	$130.1466	$130.15	$130.15	$130.10
Purchase #3	$247.49	13.750%	$281.5199	$281.52	$281.50	$281.50
Purchase #4	$71.88	9.515%	$78.7194	$78.72	$78.70	$78.70
Purchase #5	$159.41	8.318%	$172.6697	$172.67	$172.65	$172.70
Purchase #6	$115.60	4.428%	$120.7188	$120.72	$120.70	$120.70
Purchase #7	$68.40	4.637%	$71.5717	$71.57	$71.55	$71.60
7 purchase totals =	$877.55		$954.8280	$954.83	$954.75	$954.80