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	$171.69	11.717%	$191.8069	$191.81	$191.80	$191.80
Purchase #2	$206.52	4.406%	$215.6193	$215.62	$215.60	$215.60
Purchase #3	$240.83	10.362%	$265.7848	$265.78	$265.80	$265.80
Purchase #4	$94.88	11.226%	$105.5312	$105.53	$105.55	$105.50
Purchase #5	$116.54	4.823%	$122.1607	$122.16	$122.15	$122.20
Purchase #6	$85.49	7.462%	$91.8693	$91.87	$91.85	$91.90
Purchase #7	$159.75	3.106%	$164.7118	$164.71	$164.70	$164.70
7 purchase totals =	$1,075.70		$1,157.4840	$1,157.48	$1,157.45	$1,157.50