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	$143.72	4.709%	$150.4878	$150.49	$150.50	$150.50
Purchase #2	$133.94	3.376%	$138.4618	$138.46	$138.45	$138.50
Purchase #3	$72.77	8.862%	$79.2189	$79.22	$79.20	$79.20
Purchase #4	$132.44	8.773%	$144.059	$144.06	$144.05	$144.10
Purchase #5	$175.69	5.563%	$185.4636	$185.46	$185.45	$185.50
Purchase #6	$116.71	11.646%	$130.302	$130.30	$130.30	$130.30
Purchase #7	$249.56	9.658%	$273.6625	$273.66	$273.65	$273.70
7 purchase totals =	$1,024.83		$1,101.6556	$1,101.65	$1,101.60	$1,101.80