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	$68.46	8.845%	$74.5153	$74.52	$74.50	$74.50
Purchase #2	$40.73	5.673%	$43.0406	$43.04	$43.05	$43.00
Purchase #3	$231.65	3.107%	$238.8474	$238.85	$238.85	$238.80
Purchase #4	$88.56	6.821%	$94.6007	$94.60	$94.60	$94.60
Purchase #5	$236.94	12.119%	$265.6548	$265.65	$265.65	$265.70
Purchase #6	$18.95	10.398%	$20.9204	$20.92	$20.90	$20.90
Purchase #7	$27.60	4.287%	$28.7832	$28.78	$28.80	$28.80
7 purchase totals =	$712.89		$766.3624	$766.36	$766.35	$766.30