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	$87.48	3.558%	$90.5925	$90.59	$90.60	$90.60
Purchase #2	$52.68	13.749%	$59.923	$59.92	$59.90	$59.90
Purchase #3	$223.45	11.602%	$249.3747	$249.37	$249.35	$249.40
Purchase #4	$173.35	13.225%	$196.2755	$196.28	$196.30	$196.30
Purchase #5	$12.99	10.748%	$14.3862	$14.39	$14.40	$14.40
Purchase #6	$247.66	4.473%	$258.7378	$258.74	$258.75	$258.70
Purchase #7	$187.37	9.313%	$204.8198	$204.82	$204.80	$204.80
7 purchase totals =	$984.98		$1,074.1095	$1,074.11	$1,074.10	$1,074.10