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	$111.57	7.199%	$119.6019	$119.60	$119.60	$119.60
Purchase #2	$54.27	13.176%	$61.4206	$61.42	$61.40	$61.40
Purchase #3	$158.62	6.438%	$168.832	$168.83	$168.85	$168.80
Purchase #4	$133.54	8.778%	$145.2621	$145.26	$145.25	$145.30
Purchase #5	$141.52	5.570%	$149.4027	$149.40	$149.40	$149.40
Purchase #6	$91.32	4.362%	$95.3034	$95.30	$95.30	$95.30
Purchase #7	$203.31	13.664%	$231.0903	$231.09	$231.10	$231.10
7 purchase totals =	$894.15		$970.9130	$970.90	$970.90	$970.90