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	$17.40	9.469%	$19.0476	$19.05	$19.05	$19.00
Purchase #2	$235.31	9.851%	$258.4904	$258.49	$258.50	$258.50
Purchase #3	$160.67	7.141%	$172.1434	$172.14	$172.15	$172.10
Purchase #4	$68.67	8.828%	$74.7322	$74.73	$74.75	$74.70
Purchase #5	$209.63	11.701%	$234.1588	$234.16	$234.15	$234.20
Purchase #6	$232.32	13.860%	$264.5196	$264.52	$264.50	$264.50
Purchase #7	$115.81	9.724%	$127.0714	$127.07	$127.05	$127.10
7 purchase totals =	$1,039.81		$1,150.1634	$1,150.16	$1,150.15	$1,150.10