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	$42.93	4.219%	$44.7412	$44.74	$44.75	$44.70
Purchase #2	$103.60	8.333%	$112.233	$112.23	$112.25	$112.20
Purchase #3	$12.96	8.869%	$14.1094	$14.11	$14.10	$14.10
Purchase #4	$93.25	7.856%	$100.5757	$100.58	$100.60	$100.60
Purchase #5	$180.78	9.815%	$198.5236	$198.52	$198.50	$198.50
Purchase #6	$154.77	10.368%	$170.8166	$170.82	$170.80	$170.80
Purchase #7	$38.46	9.448%	$42.0937	$42.09	$42.10	$42.10
7 purchase totals =	$626.75		$683.0932	$683.09	$683.10	$683.00