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	$109.81	7.142%	$117.6526	$117.65	$117.65	$117.70
Purchase #2	$172.47	9.708%	$189.2134	$189.21	$189.20	$189.20
Purchase #3	$19.84	3.827%	$20.5993	$20.60	$20.60	$20.60
Purchase #4	$83.77	7.559%	$90.1022	$90.10	$90.10	$90.10
Purchase #5	$117.79	8.323%	$127.5937	$127.59	$127.60	$127.60
Purchase #6	$170.68	11.606%	$190.4891	$190.49	$190.50	$190.50
Purchase #7	$215.65	10.816%	$238.9747	$238.97	$238.95	$239.00
7 purchase totals =	$890.01		$974.6250	$974.61	$974.60	$974.70