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	$214.87	6.509%	$228.8559	$228.86	$228.85	$228.90
Purchase #2	$54.73	5.579%	$57.7834	$57.78	$57.80	$57.80
Purchase #3	$175.41	5.112%	$184.377	$184.38	$184.40	$184.40
Purchase #4	$93.51	11.626%	$104.3815	$104.38	$104.40	$104.40
Purchase #5	$57.33	12.302%	$64.3827	$64.38	$64.40	$64.40
Purchase #6	$176.33	10.318%	$194.5237	$194.52	$194.50	$194.50
Purchase #7	$77.57	10.120%	$85.4201	$85.42	$85.40	$85.40
7 purchase totals =	$849.75		$919.7243	$919.72	$919.75	$919.80