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	$204.86	9.640%	$224.6085	$224.61	$224.60	$224.60
Purchase #2	$133.56	9.841%	$146.7036	$146.70	$146.70	$146.70
Purchase #3	$5.77	8.598%	$6.2661	$6.27	$6.25	$6.30
Purchase #4	$225.73	6.527%	$240.4634	$240.46	$240.45	$240.50
Purchase #5	$233.90	3.826%	$242.849	$242.85	$242.85	$242.80
Purchase #6	$25.82	6.598%	$27.5236	$27.52	$27.50	$27.50
Purchase #7	$197.62	5.705%	$208.8942	$208.89	$208.90	$208.90
7 purchase totals =	$1,027.26		$1,097.3084	$1,097.30	$1,097.25	$1,097.30