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	$140.39	4.385%	$146.5461	$146.55	$146.55	$146.50
Purchase #2	$245.38	8.847%	$267.0888	$267.09	$267.10	$267.10
Purchase #3	$74.43	11.652%	$83.1026	$83.10	$83.10	$83.10
Purchase #4	$77.42	8.401%	$83.9241	$83.92	$83.90	$83.90
Purchase #5	$194.55	13.667%	$221.1391	$221.14	$221.15	$221.10
Purchase #6	$123.32	13.273%	$139.6883	$139.69	$139.70	$139.70
Purchase #7	$160.60	11.656%	$179.3195	$179.32	$179.30	$179.30
7 purchase totals =	$1,016.09		$1,120.8085	$1,120.81	$1,120.80	$1,120.70