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	$174.96	11.103%	$194.3858	$194.39	$194.40	$194.40
Purchase #2	$188.72	7.438%	$202.757	$202.76	$202.75	$202.80
Purchase #3	$89.87	11.461%	$100.17	$100.17	$100.15	$100.20
Purchase #4	$156.62	10.388%	$172.8897	$172.89	$172.90	$172.90
Purchase #5	$137.79	9.860%	$151.3761	$151.38	$151.40	$151.40
Purchase #6	$178.44	4.853%	$187.0997	$187.10	$187.10	$187.10
Purchase #7	$217.45	10.738%	$240.7998	$240.80	$240.80	$240.80
7 purchase totals =	$1,143.85		$1,249.4781	$1,249.49	$1,249.50	$1,249.60