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	$187.58	6.398%	$199.5814	$199.58	$199.60	$199.60
Purchase #2	$88.79	13.586%	$100.853	$100.85	$100.85	$100.90
Purchase #3	$160.87	3.250%	$166.0983	$166.10	$166.10	$166.10
Purchase #4	$213.83	12.443%	$240.4369	$240.44	$240.45	$240.40
Purchase #5	$119.63	3.611%	$123.9498	$123.95	$123.95	$123.90
Purchase #6	$32.49	4.396%	$33.9183	$33.92	$33.90	$33.90
Purchase #7	$228.62	10.722%	$253.1326	$253.13	$253.15	$253.10
7 purchase totals =	$1,031.81		$1,117.9703	$1,117.97	$1,118.00	$1,117.90