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	$113.56	8.618%	$123.3466	$123.35	$123.35	$123.30
Purchase #2	$174.80	8.378%	$189.4447	$189.44	$189.45	$189.40
Purchase #3	$100.60	10.464%	$111.1268	$111.13	$111.15	$111.10
Purchase #4	$15.32	11.575%	$17.0933	$17.09	$17.10	$17.10
Purchase #5	$209.59	9.865%	$230.2661	$230.27	$230.25	$230.30
Purchase #6	$136.32	10.467%	$150.5886	$150.59	$150.60	$150.60
Purchase #7	$158.94	7.701%	$171.18	$171.18	$171.20	$171.20
7 purchase totals =	$909.13		$993.0461	$993.05	$993.10	$993.00