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	$146.74	10.817%	$162.6129	$162.61	$162.60	$162.60
Purchase #2	$195.38	5.243%	$205.6238	$205.62	$205.60	$205.60
Purchase #3	$198.30	6.115%	$210.426	$210.43	$210.45	$210.40
Purchase #4	$239.35	12.456%	$269.1634	$269.16	$269.15	$269.20
Purchase #5	$194.25	11.417%	$216.4275	$216.43	$216.45	$216.40
Purchase #6	$95.83	4.435%	$100.0801	$100.08	$100.10	$100.10
Purchase #7	$162.70	5.738%	$172.0357	$172.04	$172.05	$172.00
7 purchase totals =	$1,232.55		$1,336.3694	$1,336.37	$1,336.40	$1,336.30