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	$49.84	6.471%	$53.0651	$53.07	$53.05	$53.10
Purchase #2	$232.94	6.776%	$248.724	$248.72	$248.70	$248.70
Purchase #3	$173.76	3.721%	$180.2256	$180.23	$180.25	$180.20
Purchase #4	$85.68	4.252%	$89.3231	$89.32	$89.30	$89.30
Purchase #5	$75.99	6.467%	$80.9043	$80.90	$80.90	$80.90
Purchase #6	$196.59	8.233%	$212.7753	$212.78	$212.80	$212.80
Purchase #7	$57.37	11.323%	$63.866	$63.87	$63.85	$63.90
7 purchase totals =	$872.17		$928.8834	$928.89	$928.85	$928.90