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	$156.52	12.422%	$175.9629	$175.96	$175.95	$176.00
Purchase #2	$103.58	10.306%	$114.255	$114.26	$114.25	$114.30
Purchase #3	$243.43	7.214%	$260.991	$260.99	$261.00	$261.00
Purchase #4	$184.41	6.536%	$196.463	$196.46	$196.45	$196.50
Purchase #5	$210.89	10.823%	$233.7146	$233.71	$233.70	$233.70
Purchase #6	$158.60	6.319%	$168.6219	$168.62	$168.60	$168.60
Purchase #7	$40.74	11.513%	$45.4304	$45.43	$45.45	$45.40
7 purchase totals =	$1,098.17		$1,195.4388	$1,195.43	$1,195.40	$1,195.50