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	$6.95	4.828%	$7.2855	$7.29	$7.30	$7.30
Purchase #2	$93.51	6.162%	$99.2721	$99.27	$99.25	$99.30
Purchase #3	$11.66	7.699%	$12.5577	$12.56	$12.55	$12.60
Purchase #4	$46.30	7.219%	$49.6424	$49.64	$49.65	$49.60
Purchase #5	$24.63	10.604%	$27.2418	$27.24	$27.25	$27.20
Purchase #6	$243.73	4.240%	$254.0642	$254.06	$254.05	$254.10
Purchase #7	$126.49	10.152%	$139.3313	$139.33	$139.35	$139.30
7 purchase totals =	$553.27		$589.3950	$589.39	$589.40	$589.40