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	$212.99	11.668%	$237.8417	$237.84	$237.85	$237.80
Purchase #2	$101.94	9.560%	$111.6855	$111.69	$111.70	$111.70
Purchase #3	$219.29	11.435%	$244.3658	$244.37	$244.35	$244.40
Purchase #4	$247.43	11.295%	$275.3772	$275.38	$275.40	$275.40
Purchase #5	$94.36	6.659%	$100.6434	$100.64	$100.65	$100.60
Purchase #6	$179.93	11.479%	$200.5842	$200.58	$200.60	$200.60
Purchase #7	$137.66	13.271%	$155.9289	$155.93	$155.95	$155.90
7 purchase totals =	$1,193.60		$1,326.4267	$1,326.43	$1,326.50	$1,326.40