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	$210.51	8.610%	$228.6349	$228.63	$228.65	$228.60
Purchase #2	$44.42	13.787%	$50.5442	$50.54	$50.55	$50.50
Purchase #3	$177.79	5.814%	$188.1267	$188.13	$188.15	$188.10
Purchase #4	$147.51	13.621%	$167.6023	$167.60	$167.60	$167.60
Purchase #5	$200.75	13.791%	$228.4354	$228.44	$228.45	$228.40
Purchase #6	$28.69	13.128%	$32.4564	$32.46	$32.45	$32.50
Purchase #7	$162.56	13.626%	$184.7104	$184.71	$184.70	$184.70
7 purchase totals =	$972.23		$1,080.5103	$1,080.51	$1,080.55	$1,080.40