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	$149.51	6.393%	$159.0682	$159.07	$159.05	$159.10
Purchase #2	$65.58	12.810%	$73.9808	$73.98	$74.00	$74.00
Purchase #3	$183.95	6.805%	$196.4678	$196.47	$196.45	$196.50
Purchase #4	$140.85	7.596%	$151.549	$151.55	$151.55	$151.50
Purchase #5	$44.66	9.210%	$48.7732	$48.77	$48.75	$48.80
Purchase #6	$216.41	4.215%	$225.5317	$225.53	$225.55	$225.50
Purchase #7	$214.90	5.200%	$226.0748	$226.07	$226.05	$226.10
7 purchase totals =	$1,015.86		$1,081.4455	$1,081.44	$1,081.40	$1,081.50