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	$184.88	5.260%	$194.6047	$194.60	$194.60	$194.60
Purchase #2	$47.27	9.165%	$51.6023	$51.60	$51.60	$51.60
Purchase #3	$47.94	3.727%	$49.7267	$49.73	$49.75	$49.70
Purchase #4	$51.89	4.715%	$54.3366	$54.34	$54.35	$54.30
Purchase #5	$221.78	5.686%	$234.3904	$234.39	$234.40	$234.40
Purchase #6	$109.27	13.844%	$124.3973	$124.40	$124.40	$124.40
Purchase #7	$63.42	12.658%	$71.4477	$71.45	$71.45	$71.40
7 purchase totals =	$726.45		$780.5057	$780.51	$780.55	$780.40