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	$54.29	5.527%	$57.2906	$57.29	$57.30	$57.30
Purchase #2	$93.49	8.715%	$101.6377	$101.64	$101.65	$101.60
Purchase #3	$157.88	9.120%	$172.2787	$172.28	$172.30	$172.30
Purchase #4	$149.39	13.531%	$169.604	$169.60	$169.60	$169.60
Purchase #5	$205.39	8.839%	$223.5444	$223.54	$223.55	$223.50
Purchase #6	$90.78	13.847%	$103.3503	$103.35	$103.35	$103.40
Purchase #7	$219.65	6.339%	$233.5736	$233.57	$233.55	$233.60
7 purchase totals =	$970.87		$1,061.2793	$1,061.27	$1,061.30	$1,061.30