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	$115.28	10.212%	$127.0524	$127.05	$127.05	$127.10
Purchase #2	$37.89	9.641%	$41.543	$41.54	$41.55	$41.50
Purchase #3	$11.45	12.780%	$12.9133	$12.91	$12.90	$12.90
Purchase #4	$95.98	4.874%	$100.6581	$100.66	$100.65	$100.70
Purchase #5	$197.67	9.663%	$216.7709	$216.77	$216.75	$216.80
Purchase #6	$132.29	6.778%	$141.2566	$141.26	$141.25	$141.30
Purchase #7	$195.64	12.166%	$219.4416	$219.44	$219.45	$219.40
7 purchase totals =	$786.20		$859.6359	$859.63	$859.60	$859.70