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	$165.39	13.421%	$187.587	$187.59	$187.60	$187.60
Purchase #2	$17.51	13.343%	$19.8464	$19.85	$19.85	$19.80
Purchase #3	$143.45	9.368%	$156.8884	$156.89	$156.90	$156.90
Purchase #4	$134.42	6.361%	$142.9705	$142.97	$142.95	$143.00
Purchase #5	$232.95	13.157%	$263.5992	$263.60	$263.60	$263.60
Purchase #6	$59.60	13.281%	$67.5155	$67.52	$67.50	$67.50
Purchase #7	$186.40	6.847%	$199.1628	$199.16	$199.15	$199.20
7 purchase totals =	$939.72		$1,037.5698	$1,037.58	$1,037.55	$1,037.60