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	$56.59	10.495%	$62.5291	$62.53	$62.55	$62.50
Purchase #2	$224.30	9.351%	$245.2743	$245.27	$245.25	$245.30
Purchase #3	$105.67	5.434%	$111.4121	$111.41	$111.40	$111.40
Purchase #4	$43.90	12.731%	$49.4889	$49.49	$49.50	$49.50
Purchase #5	$10.96	11.614%	$12.2329	$12.23	$12.25	$12.20
Purchase #6	$67.71	12.218%	$75.9828	$75.98	$76.00	$76.00
Purchase #7	$117.88	6.399%	$125.4231	$125.42	$125.40	$125.40
7 purchase totals =	$627.01		$682.3432	$682.33	$682.35	$682.30