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	$55.48	12.252%	$62.2774	$62.28	$62.30	$62.30
Purchase #2	$99.70	11.408%	$111.0738	$111.07	$111.05	$111.10
Purchase #3	$68.30	3.547%	$70.7226	$70.72	$70.70	$70.70
Purchase #4	$47.81	5.404%	$50.3937	$50.39	$50.40	$50.40
Purchase #5	$90.65	5.433%	$95.575	$95.58	$95.60	$95.60
Purchase #6	$167.52	10.761%	$185.5468	$185.55	$185.55	$185.50
Purchase #7	$181.55	11.366%	$202.185	$202.19	$202.20	$202.20
7 purchase totals =	$711.01		$777.7743	$777.78	$777.80	$777.80