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	$37.90	10.200%	$41.7658	$41.77	$41.75	$41.80
Purchase #2	$52.39	4.514%	$54.7549	$54.75	$54.75	$54.80
Purchase #3	$38.34	5.694%	$40.5231	$40.52	$40.50	$40.50
Purchase #4	$164.46	5.357%	$173.2701	$173.27	$173.25	$173.30
Purchase #5	$44.70	8.530%	$48.5129	$48.51	$48.50	$48.50
Purchase #6	$185.69	4.847%	$194.6904	$194.69	$194.70	$194.70
Purchase #7	$237.92	10.568%	$263.0634	$263.06	$263.05	$263.10
7 purchase totals =	$761.40		$816.5806	$816.57	$816.50	$816.70