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	$197.40	7.706%	$212.6116	$212.61	$212.60	$212.60
Purchase #2	$128.84	10.137%	$141.9005	$141.90	$141.90	$141.90
Purchase #3	$52.25	11.786%	$58.4082	$58.41	$58.40	$58.40
Purchase #4	$230.78	3.342%	$238.4927	$238.49	$238.50	$238.50
Purchase #5	$6.92	4.125%	$7.2055	$7.21	$7.20	$7.20
Purchase #6	$100.48	11.191%	$111.7247	$111.72	$111.70	$111.70
Purchase #7	$220.42	12.215%	$247.3443	$247.34	$247.35	$247.30
7 purchase totals =	$937.09		$1,017.6875	$1,017.68	$1,017.65	$1,017.60