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	$162.98	3.662%	$168.9483	$168.95	$168.95	$168.90
Purchase #2	$59.62	13.584%	$67.7188	$67.72	$67.70	$67.70
Purchase #3	$146.91	12.275%	$164.9432	$164.94	$164.95	$164.90
Purchase #4	$38.95	5.436%	$41.0673	$41.07	$41.05	$41.10
Purchase #5	$106.77	8.619%	$115.9725	$115.97	$115.95	$116.00
Purchase #6	$102.44	9.585%	$112.2589	$112.26	$112.25	$112.30
Purchase #7	$134.55	7.262%	$144.321	$144.32	$144.30	$144.30
7 purchase totals =	$752.22		$815.2300	$815.23	$815.15	$815.20