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	$225.69	8.243%	$244.2936	$244.29	$244.30	$244.30
Purchase #2	$121.65	11.840%	$136.0534	$136.05	$136.05	$136.10
Purchase #3	$158.92	9.192%	$173.5279	$173.53	$173.55	$173.50
Purchase #4	$223.38	7.461%	$240.0464	$240.05	$240.05	$240.00
Purchase #5	$168.25	3.312%	$173.8224	$173.82	$173.80	$173.80
Purchase #6	$42.87	7.214%	$45.9626	$45.96	$45.95	$46.00
Purchase #7	$32.72	3.598%	$33.8973	$33.90	$33.90	$33.90
7 purchase totals =	$973.48		$1,047.6036	$1,047.60	$1,047.60	$1,047.60