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	$54.81	8.347%	$59.385	$59.39	$59.40	$59.40
Purchase #2	$13.95	3.575%	$14.4487	$14.45	$14.45	$14.40
Purchase #3	$120.80	9.461%	$132.2289	$132.23	$132.25	$132.20
Purchase #4	$75.49	4.156%	$78.6274	$78.63	$78.65	$78.60
Purchase #5	$184.28	13.746%	$209.6111	$209.61	$209.60	$209.60
Purchase #6	$66.73	6.280%	$70.9206	$70.92	$70.90	$70.90
Purchase #7	$149.72	8.781%	$162.8669	$162.87	$162.85	$162.90
7 purchase totals =	$665.78		$728.0886	$728.10	$728.10	$728.00