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	$118.79	7.446%	$127.6351	$127.64	$127.65	$127.60
Purchase #2	$86.42	6.255%	$91.8256	$91.83	$91.85	$91.80
Purchase #3	$33.78	11.669%	$37.7218	$37.72	$37.70	$37.70
Purchase #4	$196.50	9.466%	$215.1007	$215.10	$215.10	$215.10
Purchase #5	$218.62	8.117%	$236.3654	$236.37	$236.35	$236.40
Purchase #6	$193.52	3.611%	$200.508	$200.51	$200.50	$200.50
Purchase #7	$18.26	3.776%	$18.9495	$18.95	$18.95	$18.90
7 purchase totals =	$865.89		$928.1061	$928.12	$928.10	$928.00