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	$43.66	10.615%	$48.2945	$48.29	$48.30	$48.30
Purchase #2	$96.72	11.488%	$107.8312	$107.83	$107.85	$107.80
Purchase #3	$231.54	9.590%	$253.7447	$253.74	$253.75	$253.70
Purchase #4	$159.80	6.744%	$170.5769	$170.58	$170.60	$170.60
Purchase #5	$217.56	9.517%	$238.2652	$238.27	$238.25	$238.30
Purchase #6	$50.85	8.209%	$55.0243	$55.02	$55.00	$55.00
Purchase #7	$85.63	5.790%	$90.588	$90.59	$90.60	$90.60
7 purchase totals =	$885.76		$964.3248	$964.32	$964.35	$964.30