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	$66.96	13.767%	$76.1784	$76.18	$76.20	$76.20
Purchase #2	$148.75	3.181%	$153.4817	$153.48	$153.50	$153.50
Purchase #3	$48.87	11.771%	$54.6225	$54.62	$54.60	$54.60
Purchase #4	$132.30	9.490%	$144.8553	$144.86	$144.85	$144.90
Purchase #5	$29.54	7.508%	$31.7579	$31.76	$31.75	$31.80
Purchase #6	$170.62	8.863%	$185.7421	$185.74	$185.75	$185.70
Purchase #7	$88.92	11.869%	$99.4739	$99.47	$99.45	$99.50
7 purchase totals =	$685.96		$746.1118	$746.11	$746.10	$746.20