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	$244.29	4.113%	$254.3376	$254.34	$254.35	$254.30
Purchase #2	$217.90	11.638%	$243.2592	$243.26	$243.25	$243.30
Purchase #3	$68.48	4.859%	$71.8074	$71.81	$71.80	$71.80
Purchase #4	$35.77	9.535%	$39.1807	$39.18	$39.20	$39.20
Purchase #5	$31.51	6.240%	$33.4762	$33.48	$33.50	$33.50
Purchase #6	$150.60	13.162%	$170.422	$170.42	$170.40	$170.40
Purchase #7	$47.27	10.307%	$52.1421	$52.14	$52.15	$52.10
7 purchase totals =	$795.82		$864.6252	$864.63	$864.65	$864.60