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	$133.60	11.759%	$149.31	$149.31	$149.30	$149.30
Purchase #2	$245.32	8.671%	$266.5917	$266.59	$266.60	$266.60
Purchase #3	$50.93	13.775%	$57.9456	$57.95	$57.95	$57.90
Purchase #4	$48.79	13.771%	$55.5089	$55.51	$55.50	$55.50
Purchase #5	$137.78	11.834%	$154.0849	$154.08	$154.10	$154.10
Purchase #6	$95.32	4.795%	$99.8906	$99.89	$99.90	$99.90
Purchase #7	$21.75	10.654%	$24.0672	$24.07	$24.05	$24.10
7 purchase totals =	$733.49		$807.3989	$807.40	$807.40	$807.40