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	$148.62	3.434%	$153.7236	$153.72	$153.70	$153.70
Purchase #2	$99.66	11.583%	$111.2036	$111.20	$111.20	$111.20
Purchase #3	$77.74	11.319%	$86.5394	$86.54	$86.55	$86.50
Purchase #4	$226.35	5.153%	$238.0138	$238.01	$238.00	$238.00
Purchase #5	$246.30	3.800%	$255.6594	$255.66	$255.65	$255.70
Purchase #6	$37.85	9.535%	$41.459	$41.46	$41.45	$41.50
Purchase #7	$63.50	6.103%	$67.3754	$67.38	$67.40	$67.40
7 purchase totals =	$900.02		$953.9742	$953.97	$953.95	$954.00