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	$214.54	11.183%	$238.532	$238.53	$238.55	$238.50
Purchase #2	$19.31	13.499%	$21.9167	$21.92	$21.90	$21.90
Purchase #3	$136.35	5.522%	$143.8792	$143.88	$143.90	$143.90
Purchase #4	$100.72	5.653%	$106.4137	$106.41	$106.40	$106.40
Purchase #5	$86.71	5.544%	$91.5172	$91.52	$91.50	$91.50
Purchase #6	$173.29	5.514%	$182.8452	$182.85	$182.85	$182.80
Purchase #7	$170.72	13.852%	$194.3681	$194.37	$194.35	$194.40
7 purchase totals =	$901.64		$979.4721	$979.48	$979.45	$979.40