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	$196.52	12.224%	$220.5426	$220.54	$220.55	$220.50
Purchase #2	$243.45	3.670%	$252.3846	$252.38	$252.40	$252.40
Purchase #3	$240.42	6.170%	$255.2539	$255.25	$255.25	$255.30
Purchase #4	$167.84	4.150%	$174.8054	$174.81	$174.80	$174.80
Purchase #5	$54.72	3.755%	$56.7747	$56.77	$56.75	$56.80
Purchase #6	$123.54	6.406%	$131.454	$131.45	$131.45	$131.50
Purchase #7	$178.45	11.401%	$198.7951	$198.80	$198.80	$198.80
7 purchase totals =	$1,204.94		$1,290.0103	$1,290.00	$1,290.00	$1,290.10