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	$10.30	8.647%	$11.1906	$11.19	$11.20	$11.20
Purchase #2	$49.48	3.218%	$51.0723	$51.07	$51.05	$51.10
Purchase #3	$161.91	10.767%	$179.3428	$179.34	$179.35	$179.30
Purchase #4	$156.84	10.616%	$173.4901	$173.49	$173.50	$173.50
Purchase #5	$235.76	8.176%	$255.0357	$255.04	$255.05	$255.00
Purchase #6	$96.34	7.317%	$103.3892	$103.39	$103.40	$103.40
Purchase #7	$99.75	5.583%	$105.319	$105.32	$105.30	$105.30
7 purchase totals =	$810.38		$878.8397	$878.84	$878.85	$878.80