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	$212.74	8.401%	$230.6123	$230.61	$230.60	$230.60
Purchase #2	$34.83	9.420%	$38.111	$38.11	$38.10	$38.10
Purchase #3	$216.93	11.669%	$242.2436	$242.24	$242.25	$242.20
Purchase #4	$106.90	9.738%	$117.3099	$117.31	$117.30	$117.30
Purchase #5	$106.89	4.497%	$111.6968	$111.70	$111.70	$111.70
Purchase #6	$126.56	4.501%	$132.2565	$132.26	$132.25	$132.30
Purchase #7	$73.58	6.116%	$78.0802	$78.08	$78.10	$78.10
7 purchase totals =	$878.43		$950.3103	$950.31	$950.30	$950.30