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	$14.65	12.507%	$16.4823	$16.48	$16.50	$16.50
Purchase #2	$83.78	3.778%	$86.9452	$86.95	$86.95	$86.90
Purchase #3	$67.43	7.227%	$72.3032	$72.30	$72.30	$72.30
Purchase #4	$30.76	6.248%	$32.6819	$32.68	$32.70	$32.70
Purchase #5	$171.60	9.820%	$188.4511	$188.45	$188.45	$188.50
Purchase #6	$99.68	3.436%	$103.105	$103.11	$103.10	$103.10
Purchase #7	$17.34	4.397%	$18.1024	$18.10	$18.10	$18.10
7 purchase totals =	$485.24		$518.0711	$518.07	$518.10	$518.10