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	$196.33	7.677%	$211.4023	$211.40	$211.40	$211.40
Purchase #2	$20.96	4.587%	$21.9214	$21.92	$21.90	$21.90
Purchase #3	$230.75	7.279%	$247.5463	$247.55	$247.55	$247.50
Purchase #4	$191.87	12.500%	$215.8538	$215.85	$215.85	$215.90
Purchase #5	$14.43	10.114%	$15.8895	$15.89	$15.90	$15.90
Purchase #6	$192.33	7.363%	$206.4913	$206.49	$206.50	$206.50
Purchase #7	$36.90	4.311%	$38.4908	$38.49	$38.50	$38.50
7 purchase totals =	$883.57		$957.5954	$957.59	$957.60	$957.60