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	$32.85	13.789%	$37.3797	$37.38	$37.40	$37.40
Purchase #2	$159.44	5.116%	$167.597	$167.60	$167.60	$167.60
Purchase #3	$34.37	5.623%	$36.3026	$36.30	$36.30	$36.30
Purchase #4	$245.87	9.683%	$269.6776	$269.68	$269.70	$269.70
Purchase #5	$148.65	6.552%	$158.3895	$158.39	$158.40	$158.40
Purchase #6	$132.64	13.283%	$150.2586	$150.26	$150.25	$150.30
Purchase #7	$236.59	7.810%	$255.0677	$255.07	$255.05	$255.10
7 purchase totals =	$990.41		$1,074.6727	$1,074.68	$1,074.70	$1,074.80