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	$77.77	11.677%	$86.8512	$86.85	$86.85	$86.90
Purchase #2	$87.70	4.250%	$91.4273	$91.43	$91.45	$91.40
Purchase #3	$101.83	3.165%	$105.0529	$105.05	$105.05	$105.10
Purchase #4	$132.63	4.504%	$138.6037	$138.60	$138.60	$138.60
Purchase #5	$71.27	4.259%	$74.3054	$74.31	$74.30	$74.30
Purchase #6	$36.59	7.374%	$39.2881	$39.29	$39.30	$39.30
Purchase #7	$198.34	5.333%	$208.9175	$208.92	$208.90	$208.90
7 purchase totals =	$706.13		$744.4461	$744.45	$744.45	$744.50