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	$246.46	11.874%	$275.7247	$275.72	$275.70	$275.70
Purchase #2	$250.85	10.584%	$277.4	$277.40	$277.40	$277.40
Purchase #3	$153.74	11.824%	$171.9182	$171.92	$171.90	$171.90
Purchase #4	$250.33	11.173%	$278.2994	$278.30	$278.30	$278.30
Purchase #5	$151.65	13.494%	$172.1137	$172.11	$172.10	$172.10
Purchase #6	$137.37	4.104%	$143.0077	$143.01	$143.00	$143.00
Purchase #7	$35.51	10.572%	$39.2641	$39.26	$39.25	$39.30
7 purchase totals =	$1,225.91		$1,357.7278	$1,357.72	$1,357.65	$1,357.70