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	$42.30	5.477%	$44.6168	$44.62	$44.60	$44.60
Purchase #2	$39.76	13.549%	$45.1471	$45.15	$45.15	$45.10
Purchase #3	$41.55	10.399%	$45.8708	$45.87	$45.85	$45.90
Purchase #4	$227.66	10.205%	$250.8927	$250.89	$250.90	$250.90
Purchase #5	$143.78	10.793%	$159.2982	$159.30	$159.30	$159.30
Purchase #6	$193.57	7.501%	$208.0897	$208.09	$208.10	$208.10
Purchase #7	$105.78	3.768%	$109.7658	$109.77	$109.75	$109.80
7 purchase totals =	$794.40		$863.6811	$863.69	$863.65	$863.70