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	$194.75	7.708%	$209.7613	$209.76	$209.75	$209.80
Purchase #2	$99.66	8.826%	$108.456	$108.46	$108.45	$108.50
Purchase #3	$69.63	9.716%	$76.3953	$76.40	$76.40	$76.40
Purchase #4	$127.38	10.152%	$140.3116	$140.31	$140.30	$140.30
Purchase #5	$81.61	12.341%	$91.6815	$91.68	$91.70	$91.70
Purchase #6	$183.32	9.414%	$200.5777	$200.58	$200.60	$200.60
Purchase #7	$104.56	6.523%	$111.3804	$111.38	$111.40	$111.40
7 purchase totals =	$860.91		$938.5638	$938.57	$938.60	$938.70