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	$94.66	6.349%	$100.67	$100.67	$100.65	$100.70
Purchase #2	$17.77	5.229%	$18.6992	$18.70	$18.70	$18.70
Purchase #3	$75.31	8.304%	$81.5637	$81.56	$81.55	$81.60
Purchase #4	$205.36	4.661%	$214.9318	$214.93	$214.95	$214.90
Purchase #5	$58.88	10.862%	$65.2755	$65.28	$65.30	$65.30
Purchase #6	$137.43	4.817%	$144.05	$144.05	$144.05	$144.10
Purchase #7	$167.35	3.158%	$172.6349	$172.63	$172.65	$172.60
7 purchase totals =	$756.76		$797.8251	$797.82	$797.85	$797.90