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	$94.90	8.867%	$103.3148	$103.31	$103.30	$103.30
Purchase #2	$129.74	9.389%	$141.9213	$141.92	$141.90	$141.90
Purchase #3	$49.45	12.829%	$55.7939	$55.79	$55.80	$55.80
Purchase #4	$123.90	5.227%	$130.3763	$130.38	$130.40	$130.40
Purchase #5	$120.60	9.829%	$132.4538	$132.45	$132.45	$132.50
Purchase #6	$209.72	4.810%	$219.8075	$219.81	$219.80	$219.80
Purchase #7	$143.70	13.237%	$162.7216	$162.72	$162.70	$162.70
7 purchase totals =	$872.01		$946.3892	$946.38	$946.35	$946.40