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	$221.68	12.542%	$249.4831	$249.48	$249.50	$249.50
Purchase #2	$64.39	4.462%	$67.2631	$67.26	$67.25	$67.30
Purchase #3	$11.27	7.140%	$12.0747	$12.07	$12.05	$12.10
Purchase #4	$221.51	3.779%	$229.8809	$229.88	$229.90	$229.90
Purchase #5	$185.54	4.541%	$193.9654	$193.97	$193.95	$194.00
Purchase #6	$42.45	10.275%	$46.8117	$46.81	$46.80	$46.80
Purchase #7	$29.71	10.870%	$32.9395	$32.94	$32.95	$32.90
7 purchase totals =	$776.55		$832.4184	$832.41	$832.40	$832.50