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	$95.83	13.319%	$108.5936	$108.59	$108.60	$108.60
Purchase #2	$153.64	13.413%	$174.2477	$174.25	$174.25	$174.20
Purchase #3	$225.68	5.782%	$238.7288	$238.73	$238.75	$238.70
Purchase #4	$14.79	7.328%	$15.8738	$15.87	$15.85	$15.90
Purchase #5	$130.44	12.237%	$146.4019	$146.40	$146.40	$146.40
Purchase #6	$196.50	13.630%	$223.283	$223.28	$223.30	$223.30
Purchase #7	$166.99	4.689%	$174.8202	$174.82	$174.80	$174.80
7 purchase totals =	$983.87		$1,081.9490	$1,081.94	$1,081.95	$1,081.90