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	$194.96	13.671%	$221.613	$221.61	$221.60	$221.60
Purchase #2	$106.28	7.154%	$113.8833	$113.88	$113.90	$113.90
Purchase #3	$9.32	10.689%	$10.3162	$10.32	$10.30	$10.30
Purchase #4	$46.26	6.362%	$49.2031	$49.20	$49.20	$49.20
Purchase #5	$108.54	3.583%	$112.429	$112.43	$112.45	$112.40
Purchase #6	$19.59	5.290%	$20.6263	$20.63	$20.65	$20.60
Purchase #7	$161.83	6.690%	$172.6564	$172.66	$172.65	$172.70
7 purchase totals =	$646.78		$700.7273	$700.73	$700.75	$700.70