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	$160.86	3.764%	$166.9148	$166.91	$166.90	$166.90
Purchase #2	$196.39	7.471%	$211.0623	$211.06	$211.05	$211.10
Purchase #3	$210.27	6.267%	$223.4476	$223.45	$223.45	$223.40
Purchase #4	$125.33	4.250%	$130.6565	$130.66	$130.65	$130.70
Purchase #5	$54.27	10.289%	$59.8538	$59.85	$59.85	$59.90
Purchase #6	$132.71	3.768%	$137.7105	$137.71	$137.70	$137.70
Purchase #7	$159.88	8.123%	$172.8671	$172.87	$172.85	$172.90
7 purchase totals =	$1,039.71		$1,102.5126	$1,102.51	$1,102.45	$1,102.60