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	$11.56	9.395%	$12.6461	$12.65	$12.65	$12.60
Purchase #2	$66.81	10.229%	$73.644	$73.64	$73.65	$73.60
Purchase #3	$60.66	10.258%	$66.8825	$66.88	$66.90	$66.90
Purchase #4	$11.84	5.406%	$12.4801	$12.48	$12.50	$12.50
Purchase #5	$125.75	10.214%	$138.5941	$138.59	$138.60	$138.60
Purchase #6	$85.76	5.360%	$90.3567	$90.36	$90.35	$90.40
Purchase #7	$99.92	4.296%	$104.2126	$104.21	$104.20	$104.20
7 purchase totals =	$462.30		$498.8161	$498.81	$498.85	$498.80