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	$150.53	3.592%	$155.937	$155.94	$155.95	$155.90
Purchase #2	$91.87	12.574%	$103.4217	$103.42	$103.40	$103.40
Purchase #3	$143.38	5.641%	$151.4681	$151.47	$151.45	$151.50
Purchase #4	$165.61	5.849%	$175.2965	$175.30	$175.30	$175.30
Purchase #5	$234.57	7.597%	$252.3903	$252.39	$252.40	$252.40
Purchase #6	$130.82	10.248%	$144.2264	$144.23	$144.25	$144.20
Purchase #7	$46.54	10.408%	$51.3839	$51.38	$51.40	$51.40
7 purchase totals =	$963.32		$1,034.1239	$1,034.13	$1,034.15	$1,034.10