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	$105.72	4.788%	$110.7819	$110.78	$110.80	$110.80
Purchase #2	$6.40	11.821%	$7.1565	$7.16	$7.15	$7.20
Purchase #3	$147.78	11.329%	$164.522	$164.52	$164.50	$164.50
Purchase #4	$9.57	6.807%	$10.2214	$10.22	$10.20	$10.20
Purchase #5	$77.59	6.631%	$82.735	$82.74	$82.75	$82.70
Purchase #6	$229.29	6.339%	$243.8247	$243.82	$243.80	$243.80
Purchase #7	$74.79	3.553%	$77.4473	$77.45	$77.45	$77.40
7 purchase totals =	$651.14		$696.6888	$696.69	$696.65	$696.60