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	$148.28	7.501%	$159.4025	$159.40	$159.40	$159.40
Purchase #2	$73.88	11.718%	$82.5373	$82.54	$82.55	$82.50
Purchase #3	$34.81	5.665%	$36.782	$36.78	$36.80	$36.80
Purchase #4	$54.79	3.202%	$56.5444	$56.54	$56.55	$56.50
Purchase #5	$89.37	11.613%	$99.7485	$99.75	$99.75	$99.70
Purchase #6	$71.74	8.856%	$78.0933	$78.09	$78.10	$78.10
Purchase #7	$214.93	4.301%	$224.1741	$224.17	$224.15	$224.20
7 purchase totals =	$687.80		$737.2821	$737.27	$737.30	$737.20