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	$233.58	10.584%	$258.3021	$258.30	$258.30	$258.30
Purchase #2	$47.94	5.201%	$50.4334	$50.43	$50.45	$50.40
Purchase #3	$151.41	7.246%	$162.3812	$162.38	$162.40	$162.40
Purchase #4	$68.25	7.328%	$73.2514	$73.25	$73.25	$73.30
Purchase #5	$10.83	5.261%	$11.3998	$11.40	$11.40	$11.40
Purchase #6	$158.89	8.847%	$172.947	$172.95	$172.95	$172.90
Purchase #7	$80.81	9.142%	$88.1977	$88.20	$88.20	$88.20
7 purchase totals =	$751.71		$816.9126	$816.91	$816.95	$816.90