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	$34.72	7.789%	$37.4243	$37.42	$37.40	$37.40
Purchase #2	$33.45	6.354%	$35.5754	$35.58	$35.60	$35.60
Purchase #3	$182.64	5.489%	$192.6651	$192.67	$192.65	$192.70
Purchase #4	$65.41	4.508%	$68.3587	$68.36	$68.35	$68.40
Purchase #5	$131.67	13.363%	$149.2651	$149.27	$149.25	$149.30
Purchase #6	$138.81	7.109%	$148.678	$148.68	$148.70	$148.70
Purchase #7	$80.59	12.239%	$90.4534	$90.45	$90.45	$90.50
7 purchase totals =	$667.29		$722.4200	$722.43	$722.40	$722.60