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	$37.93	11.309%	$42.2195	$42.22	$42.20	$42.20
Purchase #2	$47.72	10.549%	$52.754	$52.75	$52.75	$52.80
Purchase #3	$176.38	13.173%	$199.6145	$199.61	$199.60	$199.60
Purchase #4	$234.78	11.869%	$262.646	$262.65	$262.65	$262.60
Purchase #5	$86.77	3.461%	$89.7731	$89.77	$89.75	$89.80
Purchase #6	$213.97	5.354%	$225.426	$225.43	$225.45	$225.40
Purchase #7	$175.47	9.783%	$192.6362	$192.64	$192.65	$192.60
7 purchase totals =	$973.02		$1,065.0693	$1,065.07	$1,065.05	$1,065.00