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	$43.51	7.596%	$46.815	$46.82	$46.80	$46.80
Purchase #2	$36.82	10.256%	$40.5963	$40.60	$40.60	$40.60
Purchase #3	$197.94	13.555%	$224.7708	$224.77	$224.75	$224.80
Purchase #4	$133.66	12.379%	$150.2058	$150.21	$150.20	$150.20
Purchase #5	$17.59	8.410%	$19.0693	$19.07	$19.05	$19.10
Purchase #6	$72.89	13.683%	$82.8635	$82.86	$82.85	$82.90
Purchase #7	$195.81	8.298%	$212.0583	$212.06	$212.05	$212.10
7 purchase totals =	$698.22		$776.3790	$776.39	$776.30	$776.50