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	$203.92	6.150%	$216.4611	$216.46	$216.45	$216.50
Purchase #2	$63.39	3.485%	$65.5991	$65.60	$65.60	$65.60
Purchase #3	$60.45	5.409%	$63.7197	$63.72	$63.70	$63.70
Purchase #4	$126.26	13.567%	$143.3897	$143.39	$143.40	$143.40
Purchase #5	$204.74	8.145%	$221.4161	$221.42	$221.40	$221.40
Purchase #6	$69.65	3.790%	$72.2897	$72.29	$72.30	$72.30
Purchase #7	$214.33	3.666%	$222.1873	$222.19	$222.20	$222.20
7 purchase totals =	$942.74		$1,005.0627	$1,005.07	$1,005.05	$1,005.10