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	$23.28	4.463%	$24.319	$24.32	$24.30	$24.30
Purchase #2	$123.88	9.171%	$135.241	$135.24	$135.25	$135.20
Purchase #3	$212.29	11.202%	$236.0707	$236.07	$236.05	$236.10
Purchase #4	$85.61	3.391%	$88.513	$88.51	$88.50	$88.50
Purchase #5	$222.94	4.786%	$233.6099	$233.61	$233.60	$233.60
Purchase #6	$102.98	8.533%	$111.7673	$111.77	$111.75	$111.80
Purchase #7	$58.96	11.166%	$65.5435	$65.54	$65.55	$65.50
7 purchase totals =	$829.94		$895.0644	$895.06	$895.00	$895.00