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	$172.45	9.534%	$188.8914	$188.89	$188.90	$188.90
Purchase #2	$95.40	8.780%	$103.7761	$103.78	$103.80	$103.80
Purchase #3	$7.60	10.223%	$8.3769	$8.38	$8.40	$8.40
Purchase #4	$182.49	12.787%	$205.825	$205.83	$205.85	$205.80
Purchase #5	$226.90	7.820%	$244.6436	$244.64	$244.65	$244.60
Purchase #6	$49.61	5.848%	$52.5112	$52.51	$52.50	$52.50
Purchase #7	$189.79	11.116%	$210.8871	$210.89	$210.90	$210.90
7 purchase totals =	$924.24		$1,014.9113	$1,014.92	$1,015.00	$1,014.90