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	$227.88	6.275%	$242.1795	$242.18	$242.20	$242.20
Purchase #2	$56.72	7.670%	$61.0704	$61.07	$61.05	$61.10
Purchase #3	$238.68	7.154%	$255.7552	$255.76	$255.75	$255.80
Purchase #4	$189.77	3.411%	$196.2431	$196.24	$196.25	$196.20
Purchase #5	$63.94	7.619%	$68.8116	$68.81	$68.80	$68.80
Purchase #6	$190.27	3.286%	$196.5223	$196.52	$196.50	$196.50
Purchase #7	$205.30	4.426%	$214.3866	$214.39	$214.40	$214.40
7 purchase totals =	$1,172.56		$1,234.9687	$1,234.97	$1,234.95	$1,235.00