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	$149.30	7.222%	$160.0824	$160.08	$160.10	$160.10
Purchase #2	$48.51	8.589%	$52.6765	$52.68	$52.70	$52.70
Purchase #3	$250.85	7.870%	$270.5919	$270.59	$270.60	$270.60
Purchase #4	$54.39	12.198%	$61.0245	$61.02	$61.00	$61.00
Purchase #5	$151.66	10.557%	$167.6707	$167.67	$167.65	$167.70
Purchase #6	$99.41	12.422%	$111.7587	$111.76	$111.75	$111.80
Purchase #7	$227.34	5.736%	$240.3802	$240.38	$240.40	$240.40
7 purchase totals =	$981.46		$1,064.1849	$1,064.18	$1,064.20	$1,064.30