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	$126.70	13.181%	$143.4003	$143.40	$143.40	$143.40
Purchase #2	$35.97	13.162%	$40.7044	$40.70	$40.70	$40.70
Purchase #3	$68.78	5.742%	$72.7293	$72.73	$72.75	$72.70
Purchase #4	$200.79	13.718%	$228.3344	$228.33	$228.35	$228.30
Purchase #5	$99.51	12.180%	$111.6303	$111.63	$111.65	$111.60
Purchase #6	$47.46	5.558%	$50.0978	$50.10	$50.10	$50.10
Purchase #7	$121.33	4.761%	$127.1065	$127.11	$127.10	$127.10
7 purchase totals =	$700.54		$774.0030	$774.00	$774.05	$773.90