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	$40.45	9.459%	$44.2762	$44.28	$44.30	$44.30
Purchase #2	$101.30	10.223%	$111.6559	$111.66	$111.65	$111.70
Purchase #3	$51.53	5.708%	$54.4713	$54.47	$54.45	$54.50
Purchase #4	$84.84	6.797%	$90.6066	$90.61	$90.60	$90.60
Purchase #5	$14.99	5.862%	$15.8687	$15.87	$15.85	$15.90
Purchase #6	$86.36	11.236%	$96.0634	$96.06	$96.05	$96.10
Purchase #7	$66.87	11.556%	$74.5975	$74.60	$74.60	$74.60
7 purchase totals =	$446.34		$487.5396	$487.55	$487.50	$487.70