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	$92.94	8.499%	$100.839	$100.84	$100.85	$100.80
Purchase #2	$146.83	12.574%	$165.2924	$165.29	$165.30	$165.30
Purchase #3	$177.45	9.120%	$193.6334	$193.63	$193.65	$193.60
Purchase #4	$158.82	6.358%	$168.9178	$168.92	$168.90	$168.90
Purchase #5	$183.90	3.841%	$190.9636	$190.96	$190.95	$191.00
Purchase #6	$106.69	4.183%	$111.1528	$111.15	$111.15	$111.20
Purchase #7	$21.85	9.414%	$23.907	$23.91	$23.90	$23.90
7 purchase totals =	$888.48		$954.7060	$954.70	$954.70	$954.70