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	$175.26	8.552%	$190.2482	$190.25	$190.25	$190.20
Purchase #2	$79.91	13.284%	$90.5252	$90.53	$90.55	$90.50
Purchase #3	$227.26	11.665%	$253.7699	$253.77	$253.75	$253.80
Purchase #4	$213.52	4.337%	$222.7804	$222.78	$222.80	$222.80
Purchase #5	$103.70	8.278%	$112.2843	$112.28	$112.30	$112.30
Purchase #6	$45.56	13.220%	$51.583	$51.58	$51.60	$51.60
Purchase #7	$108.63	8.427%	$117.7843	$117.78	$117.80	$117.80
7 purchase totals =	$953.84		$1,038.9753	$1,038.97	$1,039.05	$1,039.00