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	$140.53	5.716%	$148.5627	$148.56	$148.55	$148.60
Purchase #2	$135.60	5.671%	$143.2899	$143.29	$143.30	$143.30
Purchase #3	$163.91	13.787%	$186.5083	$186.51	$186.50	$186.50
Purchase #4	$205.65	7.694%	$221.4727	$221.47	$221.45	$221.50
Purchase #5	$235.58	6.470%	$250.822	$250.82	$250.80	$250.80
Purchase #6	$32.25	4.227%	$33.6132	$33.61	$33.60	$33.60
Purchase #7	$170.93	13.643%	$194.25	$194.25	$194.25	$194.30
7 purchase totals =	$1,084.45		$1,178.5188	$1,178.51	$1,178.45	$1,178.60