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	$39.25	12.819%	$44.2815	$44.28	$44.30	$44.30
Purchase #2	$65.27	11.502%	$72.7774	$72.78	$72.80	$72.80
Purchase #3	$197.90	3.155%	$204.1437	$204.14	$204.15	$204.10
Purchase #4	$32.50	10.163%	$35.803	$35.80	$35.80	$35.80
Purchase #5	$153.66	8.228%	$166.3031	$166.30	$166.30	$166.30
Purchase #6	$110.62	5.245%	$116.422	$116.42	$116.40	$116.40
Purchase #7	$25.76	6.237%	$27.3667	$27.37	$27.35	$27.40
7 purchase totals =	$624.96		$667.0974	$667.09	$667.10	$667.10