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	$173.95	9.831%	$191.051	$191.05	$191.05	$191.10
Purchase #2	$247.45	8.205%	$267.7533	$267.75	$267.75	$267.80
Purchase #3	$151.94	4.729%	$159.1252	$159.13	$159.15	$159.10
Purchase #4	$238.40	7.173%	$255.5004	$255.50	$255.50	$255.50
Purchase #5	$169.70	9.501%	$185.8232	$185.82	$185.80	$185.80
Purchase #6	$18.90	11.801%	$21.1304	$21.13	$21.15	$21.10
Purchase #7	$29.67	9.551%	$32.5038	$32.50	$32.50	$32.50
7 purchase totals =	$1,030.01		$1,112.8873	$1,112.88	$1,112.90	$1,112.90