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	$132.60	9.695%	$145.4556	$145.46	$145.45	$145.50
Purchase #2	$71.60	6.855%	$76.5082	$76.51	$76.50	$76.50
Purchase #3	$129.89	12.302%	$145.8691	$145.87	$145.85	$145.90
Purchase #4	$133.64	6.815%	$142.7476	$142.75	$142.75	$142.70
Purchase #5	$73.73	9.125%	$80.4579	$80.46	$80.45	$80.50
Purchase #6	$33.43	8.549%	$36.2879	$36.29	$36.30	$36.30
Purchase #7	$43.39	5.633%	$45.8342	$45.83	$45.85	$45.80
7 purchase totals =	$618.28		$673.1605	$673.17	$673.15	$673.20