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	$169.82	10.862%	$188.2658	$188.27	$188.25	$188.30
Purchase #2	$98.40	9.488%	$107.7362	$107.74	$107.75	$107.70
Purchase #3	$80.87	11.495%	$90.166	$90.17	$90.15	$90.20
Purchase #4	$136.64	11.196%	$151.9382	$151.94	$151.95	$151.90
Purchase #5	$122.95	5.816%	$130.1008	$130.10	$130.10	$130.10
Purchase #6	$189.43	5.820%	$200.4548	$200.45	$200.45	$200.50
Purchase #7	$209.52	13.136%	$237.0425	$237.04	$237.05	$237.00
7 purchase totals =	$1,007.63		$1,105.7043	$1,105.71	$1,105.70	$1,105.70