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	$101.74	7.613%	$109.4855	$109.49	$109.50	$109.50
Purchase #2	$221.74	11.220%	$246.6192	$246.62	$246.60	$246.60
Purchase #3	$59.80	7.528%	$64.3017	$64.30	$64.30	$64.30
Purchase #4	$177.37	7.739%	$191.0967	$191.10	$191.10	$191.10
Purchase #5	$146.59	10.254%	$161.6213	$161.62	$161.60	$161.60
Purchase #6	$39.64	6.671%	$42.2844	$42.28	$42.30	$42.30
Purchase #7	$102.42	3.337%	$105.8378	$105.84	$105.85	$105.80
7 purchase totals =	$849.30		$921.2466	$921.25	$921.25	$921.20