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	$80.75	7.105%	$86.4873	$86.49	$86.50	$86.50
Purchase #2	$44.81	13.366%	$50.7993	$50.80	$50.80	$50.80
Purchase #3	$248.82	13.205%	$281.6767	$281.68	$281.70	$281.70
Purchase #4	$120.91	11.484%	$134.7953	$134.80	$134.80	$134.80
Purchase #5	$183.71	3.827%	$190.7406	$190.74	$190.75	$190.70
Purchase #6	$56.99	3.561%	$59.0194	$59.02	$59.00	$59.00
Purchase #7	$242.44	8.494%	$263.0329	$263.03	$263.05	$263.00
7 purchase totals =	$978.43		$1,066.5515	$1,066.56	$1,066.60	$1,066.50