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	$41.41	4.312%	$43.1956	$43.20	$43.20	$43.20
Purchase #2	$53.38	11.513%	$59.5256	$59.53	$59.55	$59.50
Purchase #3	$150.58	5.281%	$158.5321	$158.53	$158.55	$158.50
Purchase #4	$12.27	8.497%	$13.3126	$13.31	$13.30	$13.30
Purchase #5	$128.58	8.564%	$139.5916	$139.59	$139.60	$139.60
Purchase #6	$214.77	8.756%	$233.5753	$233.58	$233.60	$233.60
Purchase #7	$133.96	13.317%	$151.7995	$151.80	$151.80	$151.80
7 purchase totals =	$734.95		$799.5323	$799.54	$799.60	$799.50