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	$134.56	13.752%	$153.0647	$153.06	$153.05	$153.10
Purchase #2	$186.51	12.272%	$209.3985	$209.40	$209.40	$209.40
Purchase #3	$109.66	12.658%	$123.5408	$123.54	$123.55	$123.50
Purchase #4	$151.91	4.643%	$158.9632	$158.96	$158.95	$159.00
Purchase #5	$52.72	13.716%	$59.9511	$59.95	$59.95	$60.00
Purchase #6	$104.81	11.360%	$116.7164	$116.72	$116.70	$116.70
Purchase #7	$134.26	9.668%	$147.2403	$147.24	$147.25	$147.20
7 purchase totals =	$874.43		$968.8750	$968.87	$968.85	$968.90