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	$53.89	11.414%	$60.041	$60.04	$60.05	$60.00
Purchase #2	$81.82	10.747%	$90.6132	$90.61	$90.60	$90.60
Purchase #3	$170.39	8.726%	$185.2582	$185.26	$185.25	$185.30
Purchase #4	$150.49	3.848%	$156.2809	$156.28	$156.30	$156.30
Purchase #5	$103.65	12.246%	$116.343	$116.34	$116.35	$116.30
Purchase #6	$48.39	11.825%	$54.1121	$54.11	$54.10	$54.10
Purchase #7	$200.83	9.438%	$219.7843	$219.78	$219.80	$219.80
7 purchase totals =	$809.46		$882.4327	$882.42	$882.45	$882.40