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	$108.56	8.840%	$118.1567	$118.16	$118.15	$118.20
Purchase #2	$154.32	3.743%	$160.0962	$160.10	$160.10	$160.10
Purchase #3	$225.43	4.142%	$234.7673	$234.77	$234.75	$234.80
Purchase #4	$34.96	13.435%	$39.6569	$39.66	$39.65	$39.70
Purchase #5	$235.86	8.649%	$256.2595	$256.26	$256.25	$256.30
Purchase #6	$152.31	4.687%	$159.4488	$159.45	$159.45	$159.40
Purchase #7	$89.83	9.777%	$98.6127	$98.61	$98.60	$98.60
7 purchase totals =	$1,001.27		$1,066.9981	$1,067.01	$1,066.95	$1,067.10