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	$113.70	12.225%	$127.5998	$127.60	$127.60	$127.60
Purchase #2	$187.30	13.259%	$212.1341	$212.13	$212.15	$212.10
Purchase #3	$230.35	5.809%	$243.731	$243.73	$243.75	$243.70
Purchase #4	$128.85	8.187%	$139.3989	$139.40	$139.40	$139.40
Purchase #5	$222.28	4.352%	$231.9536	$231.95	$231.95	$232.00
Purchase #6	$15.38	6.272%	$16.3446	$16.34	$16.35	$16.30
Purchase #7	$213.64	5.253%	$224.8625	$224.86	$224.85	$224.90
7 purchase totals =	$1,111.50		$1,196.0245	$1,196.01	$1,196.05	$1,196.00