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	$157.55	9.229%	$172.0903	$172.09	$172.10	$172.10
Purchase #2	$136.83	11.450%	$152.497	$152.50	$152.50	$152.50
Purchase #3	$149.95	10.745%	$166.0621	$166.06	$166.05	$166.10
Purchase #4	$147.69	7.549%	$158.8391	$158.84	$158.85	$158.80
Purchase #5	$57.69	4.662%	$60.3795	$60.38	$60.40	$60.40
Purchase #6	$172.28	8.751%	$187.3562	$187.36	$187.35	$187.40
Purchase #7	$194.39	7.396%	$208.7671	$208.77	$208.75	$208.80
7 purchase totals =	$1,016.38		$1,105.9913	$1,106.00	$1,106.00	$1,106.10