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	$244.27	5.868%	$258.6038	$258.60	$258.60	$258.60
Purchase #2	$79.43	5.727%	$83.979	$83.98	$84.00	$84.00
Purchase #3	$148.86	4.153%	$155.0422	$155.04	$155.05	$155.00
Purchase #4	$152.81	13.181%	$172.9519	$172.95	$172.95	$173.00
Purchase #5	$127.71	11.563%	$142.4771	$142.48	$142.50	$142.50
Purchase #6	$240.42	4.378%	$250.9456	$250.95	$250.95	$250.90
Purchase #7	$20.72	8.652%	$22.5127	$22.51	$22.50	$22.50
7 purchase totals =	$1,014.22		$1,086.5123	$1,086.51	$1,086.55	$1,086.50