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	$113.33	3.617%	$117.4291	$117.43	$117.45	$117.40
Purchase #2	$33.28	4.332%	$34.7217	$34.72	$34.70	$34.70
Purchase #3	$41.33	10.104%	$45.506	$45.51	$45.50	$45.50
Purchase #4	$174.66	12.454%	$196.4122	$196.41	$196.40	$196.40
Purchase #5	$99.40	3.335%	$102.715	$102.72	$102.70	$102.70
Purchase #6	$157.75	5.141%	$165.8599	$165.86	$165.85	$165.90
Purchase #7	$228.37	6.422%	$243.0359	$243.04	$243.05	$243.00
7 purchase totals =	$848.12		$905.6798	$905.69	$905.65	$905.60