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	$41.47	10.327%	$45.7526	$45.75	$45.75	$45.80
Purchase #2	$53.88	10.723%	$59.6576	$59.66	$59.65	$59.70
Purchase #3	$178.89	6.479%	$190.4803	$190.48	$190.50	$190.50
Purchase #4	$83.71	12.139%	$93.8716	$93.87	$93.85	$93.90
Purchase #5	$222.95	6.854%	$238.231	$238.23	$238.25	$238.20
Purchase #6	$218.28	4.700%	$228.5392	$228.54	$228.55	$228.50
Purchase #7	$96.45	6.858%	$103.0645	$103.06	$103.05	$103.10
7 purchase totals =	$895.63		$959.5968	$959.59	$959.60	$959.70