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	$204.61	3.389%	$211.5442	$211.54	$211.55	$211.50
Purchase #2	$30.38	5.374%	$32.0126	$32.01	$32.00	$32.00
Purchase #3	$167.61	9.514%	$183.5564	$183.56	$183.55	$183.60
Purchase #4	$143.93	9.346%	$157.3817	$157.38	$157.40	$157.40
Purchase #5	$90.73	10.468%	$100.2276	$100.23	$100.25	$100.20
Purchase #6	$79.34	5.660%	$83.8306	$83.83	$83.85	$83.80
Purchase #7	$105.82	11.692%	$118.1925	$118.19	$118.20	$118.20
7 purchase totals =	$822.42		$886.7456	$886.74	$886.80	$886.70