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	$118.89	10.236%	$131.0596	$131.06	$131.05	$131.10
Purchase #2	$32.32	5.870%	$34.2172	$34.22	$34.20	$34.20
Purchase #3	$71.59	13.416%	$81.1945	$81.19	$81.20	$81.20
Purchase #4	$88.74	3.210%	$91.5886	$91.59	$91.60	$91.60
Purchase #5	$223.74	10.588%	$247.4296	$247.43	$247.45	$247.40
Purchase #6	$45.31	11.455%	$50.5003	$50.50	$50.50	$50.50
Purchase #7	$50.33	11.406%	$56.0706	$56.07	$56.05	$56.10
7 purchase totals =	$630.92		$692.0604	$692.06	$692.05	$692.10