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	$132.26	9.833%	$145.2651	$145.27	$145.25	$145.30
Purchase #2	$122.66	13.364%	$139.0523	$139.05	$139.05	$139.10
Purchase #3	$72.88	12.609%	$82.0694	$82.07	$82.05	$82.10
Purchase #4	$231.49	10.537%	$255.8821	$255.88	$255.90	$255.90
Purchase #5	$67.76	5.727%	$71.6406	$71.64	$71.65	$71.60
Purchase #6	$140.54	4.329%	$146.624	$146.62	$146.60	$146.60
Purchase #7	$67.42	8.224%	$72.9646	$72.96	$72.95	$73.00
7 purchase totals =	$835.01		$913.4981	$913.49	$913.45	$913.60