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	$200.53	6.116%	$212.7944	$212.79	$212.80	$212.80
Purchase #2	$88.28	3.791%	$91.6267	$91.63	$91.65	$91.60
Purchase #3	$78.35	5.326%	$82.5229	$82.52	$82.50	$82.50
Purchase #4	$88.95	12.821%	$100.3543	$100.35	$100.35	$100.40
Purchase #5	$127.40	13.609%	$144.7379	$144.74	$144.75	$144.70
Purchase #6	$239.74	4.389%	$250.2622	$250.26	$250.25	$250.30
Purchase #7	$138.78	10.862%	$153.8543	$153.85	$153.85	$153.90
7 purchase totals =	$962.03		$1,036.1527	$1,036.14	$1,036.15	$1,036.20