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	$100.84	4.862%	$105.7428	$105.74	$105.75	$105.70
Purchase #2	$135.81	12.706%	$153.066	$153.07	$153.05	$153.10
Purchase #3	$113.43	12.413%	$127.5101	$127.51	$127.50	$127.50
Purchase #4	$137.72	4.730%	$144.2342	$144.23	$144.25	$144.20
Purchase #5	$19.72	8.542%	$21.4045	$21.40	$21.40	$21.40
Purchase #6	$241.25	11.198%	$268.2652	$268.27	$268.25	$268.30
Purchase #7	$78.86	13.560%	$89.5534	$89.55	$89.55	$89.60
7 purchase totals =	$827.63		$909.7762	$909.77	$909.75	$909.80