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	$144.40	4.857%	$151.4135	$151.41	$151.40	$151.40
Purchase #2	$113.46	5.288%	$119.4598	$119.46	$119.45	$119.50
Purchase #3	$157.39	4.777%	$164.9085	$164.91	$164.90	$164.90
Purchase #4	$59.97	4.444%	$62.6351	$62.64	$62.65	$62.60
Purchase #5	$95.71	10.510%	$105.7691	$105.77	$105.75	$105.80
Purchase #6	$49.50	8.711%	$53.8119	$53.81	$53.80	$53.80
Purchase #7	$235.32	12.860%	$265.5822	$265.58	$265.60	$265.60
7 purchase totals =	$855.75		$923.5801	$923.58	$923.55	$923.60