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	$217.97	6.132%	$231.3359	$231.34	$231.35	$231.30
Purchase #2	$35.97	10.849%	$39.8724	$39.87	$39.85	$39.90
Purchase #3	$40.34	4.177%	$42.025	$42.03	$42.05	$42.00
Purchase #4	$127.33	3.406%	$131.6669	$131.67	$131.65	$131.70
Purchase #5	$123.71	3.250%	$127.7306	$127.73	$127.75	$127.70
Purchase #6	$70.68	9.389%	$77.3161	$77.32	$77.30	$77.30
Purchase #7	$45.50	3.428%	$47.0597	$47.06	$47.05	$47.10
7 purchase totals =	$661.50		$697.0066	$697.02	$697.00	$697.00