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	$71.51	5.295%	$75.2965	$75.30	$75.30	$75.30
Purchase #2	$140.50	9.264%	$153.5159	$153.52	$153.50	$153.50
Purchase #3	$246.57	9.250%	$269.3777	$269.38	$269.40	$269.40
Purchase #4	$245.64	10.496%	$271.4224	$271.42	$271.40	$271.40
Purchase #5	$249.81	12.324%	$280.5966	$280.60	$280.60	$280.60
Purchase #6	$196.46	4.312%	$204.9314	$204.93	$204.95	$204.90
Purchase #7	$80.92	11.655%	$90.3512	$90.35	$90.35	$90.40
7 purchase totals =	$1,231.41		$1,345.4917	$1,345.50	$1,345.50	$1,345.50