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	$153.88	11.462%	$171.5177	$171.52	$171.50	$171.50
Purchase #2	$98.75	7.693%	$106.3468	$106.35	$106.35	$106.30
Purchase #3	$123.76	7.466%	$132.9999	$133.00	$133.00	$133.00
Purchase #4	$49.95	7.217%	$53.5549	$53.55	$53.55	$53.60
Purchase #5	$18.68	11.488%	$20.826	$20.83	$20.85	$20.80
Purchase #6	$173.82	9.745%	$190.7588	$190.76	$190.75	$190.80
Purchase #7	$65.66	7.131%	$70.3422	$70.34	$70.35	$70.30
7 purchase totals =	$684.50		$746.3463	$746.35	$746.35	$746.30