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	$96.45	9.702%	$105.8076	$105.81	$105.80	$105.80
Purchase #2	$77.48	13.836%	$88.2001	$88.20	$88.20	$88.20
Purchase #3	$137.47	9.397%	$150.3881	$150.39	$150.40	$150.40
Purchase #4	$54.25	7.191%	$58.1511	$58.15	$58.15	$58.20
Purchase #5	$73.68	11.463%	$82.1259	$82.13	$82.15	$82.10
Purchase #6	$200.96	12.162%	$225.4008	$225.40	$225.40	$225.40
Purchase #7	$132.46	6.739%	$141.3865	$141.39	$141.40	$141.40
7 purchase totals =	$772.75		$851.4601	$851.47	$851.50	$851.50