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	$101.44	4.558%	$106.0636	$106.06	$106.05	$106.10
Purchase #2	$60.32	13.593%	$68.5193	$68.52	$68.50	$68.50
Purchase #3	$107.26	4.275%	$111.8454	$111.85	$111.85	$111.80
Purchase #4	$32.43	4.688%	$33.9503	$33.95	$33.95	$34.00
Purchase #5	$96.45	9.356%	$105.4739	$105.47	$105.45	$105.50
Purchase #6	$172.61	9.578%	$189.1426	$189.14	$189.15	$189.10
Purchase #7	$110.63	11.483%	$123.3336	$123.33	$123.35	$123.30
7 purchase totals =	$681.14		$738.3287	$738.32	$738.30	$738.30