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	$147.32	11.706%	$164.5653	$164.57	$164.55	$164.60
Purchase #2	$190.83	5.169%	$200.694	$200.69	$200.70	$200.70
Purchase #3	$209.26	12.443%	$235.2982	$235.30	$235.30	$235.30
Purchase #4	$129.94	6.146%	$137.9261	$137.93	$137.95	$137.90
Purchase #5	$101.46	9.827%	$111.4305	$111.43	$111.45	$111.40
Purchase #6	$80.89	13.640%	$91.9234	$91.92	$91.90	$91.90
Purchase #7	$161.25	8.534%	$175.0111	$175.01	$175.00	$175.00
7 purchase totals =	$1,020.95		$1,116.8486	$1,116.85	$1,116.85	$1,116.80