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	$173.34	10.460%	$191.4714	$191.47	$191.45	$191.50
Purchase #2	$95.65	3.669%	$99.1594	$99.16	$99.15	$99.20
Purchase #3	$168.64	4.381%	$176.0281	$176.03	$176.05	$176.00
Purchase #4	$95.77	5.346%	$100.8899	$100.89	$100.90	$100.90
Purchase #5	$149.69	4.485%	$156.4036	$156.40	$156.40	$156.40
Purchase #6	$179.53	10.747%	$198.8241	$198.82	$198.80	$198.80
Purchase #7	$10.27	13.755%	$11.6826	$11.68	$11.70	$11.70
7 purchase totals =	$872.89		$934.4591	$934.45	$934.45	$934.50