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	$226.28	5.198%	$238.042	$238.04	$238.05	$238.00
Purchase #2	$82.82	9.231%	$90.4651	$90.47	$90.45	$90.50
Purchase #3	$109.83	4.113%	$114.3473	$114.35	$114.35	$114.30
Purchase #4	$200.87	11.855%	$224.6831	$224.68	$224.70	$224.70
Purchase #5	$84.47	11.651%	$94.3116	$94.31	$94.30	$94.30
Purchase #6	$18.83	7.113%	$20.1694	$20.17	$20.15	$20.20
Purchase #7	$34.86	13.402%	$39.5319	$39.53	$39.55	$39.50
7 purchase totals =	$757.96		$821.5504	$821.55	$821.55	$821.50