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	$189.61	5.694%	$200.4064	$200.41	$200.40	$200.40
Purchase #2	$60.92	8.547%	$66.1268	$66.13	$66.15	$66.10
Purchase #3	$158.34	9.739%	$173.7607	$173.76	$173.75	$173.80
Purchase #4	$100.49	3.127%	$103.6323	$103.63	$103.65	$103.60
Purchase #5	$216.65	3.126%	$223.4225	$223.42	$223.40	$223.40
Purchase #6	$153.84	5.699%	$162.6073	$162.61	$162.60	$162.60
Purchase #7	$161.98	8.319%	$175.4551	$175.46	$175.45	$175.50
7 purchase totals =	$1,041.83		$1,105.4111	$1,105.42	$1,105.40	$1,105.40