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	$22.41	10.663%	$24.7996	$24.80	$24.80	$24.80
Purchase #2	$200.28	9.293%	$218.892	$218.89	$218.90	$218.90
Purchase #3	$214.71	6.491%	$228.6468	$228.65	$228.65	$228.60
Purchase #4	$39.46	4.294%	$41.1544	$41.15	$41.15	$41.20
Purchase #5	$98.28	3.305%	$101.5282	$101.53	$101.55	$101.50
Purchase #6	$53.88	10.716%	$59.6538	$59.65	$59.65	$59.70
Purchase #7	$49.57	6.637%	$52.86	$52.86	$52.85	$52.90
7 purchase totals =	$678.59		$727.5348	$727.53	$727.55	$727.60