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	$30.97	4.800%	$32.4566	$32.46	$32.45	$32.50
Purchase #2	$42.74	4.194%	$44.5325	$44.53	$44.55	$44.50
Purchase #3	$87.54	9.737%	$96.0638	$96.06	$96.05	$96.10
Purchase #4	$245.94	4.204%	$256.2793	$256.28	$256.30	$256.30
Purchase #5	$38.56	8.816%	$41.9594	$41.96	$41.95	$42.00
Purchase #6	$175.83	5.213%	$184.996	$185.00	$185.00	$185.00
Purchase #7	$132.74	9.766%	$145.7034	$145.70	$145.70	$145.70
7 purchase totals =	$754.32		$801.9910	$801.99	$802.00	$802.10