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	$76.95	5.273%	$81.0076	$81.01	$81.00	$81.00
Purchase #2	$163.52	13.404%	$185.4382	$185.44	$185.45	$185.40
Purchase #3	$68.56	4.132%	$71.3929	$71.39	$71.40	$71.40
Purchase #4	$105.43	5.796%	$111.5407	$111.54	$111.55	$111.50
Purchase #5	$23.75	6.468%	$25.2862	$25.29	$25.30	$25.30
Purchase #6	$204.49	7.612%	$220.0558	$220.06	$220.05	$220.10
Purchase #7	$23.86	7.332%	$25.6094	$25.61	$25.60	$25.60
7 purchase totals =	$666.56		$720.3308	$720.34	$720.35	$720.30