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	$11.85	3.496%	$12.2643	$12.26	$12.25	$12.30
Purchase #2	$155.93	13.320%	$176.6999	$176.70	$176.70	$176.70
Purchase #3	$226.41	12.729%	$255.2297	$255.23	$255.25	$255.20
Purchase #4	$17.74	11.705%	$19.8165	$19.82	$19.80	$19.80
Purchase #5	$85.92	3.824%	$89.2056	$89.21	$89.20	$89.20
Purchase #6	$59.99	9.845%	$65.896	$65.90	$65.90	$65.90
Purchase #7	$133.37	12.693%	$150.2987	$150.30	$150.30	$150.30
7 purchase totals =	$691.21		$769.4107	$769.42	$769.40	$769.40