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	$209.40	6.420%	$222.8435	$222.84	$222.85	$222.80
Purchase #2	$102.88	4.780%	$107.7977	$107.80	$107.80	$107.80
Purchase #3	$141.52	8.624%	$153.7247	$153.72	$153.70	$153.70
Purchase #4	$73.68	11.313%	$82.0154	$82.02	$82.00	$82.00
Purchase #5	$211.88	13.188%	$239.8227	$239.82	$239.80	$239.80
Purchase #6	$100.55	4.587%	$105.1622	$105.16	$105.15	$105.20
Purchase #7	$45.74	11.179%	$50.8533	$50.85	$50.85	$50.90
7 purchase totals =	$885.65		$962.2195	$962.21	$962.15	$962.20