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	$130.26	8.119%	$140.8358	$140.84	$140.85	$140.80
Purchase #2	$48.27	11.576%	$53.8577	$53.86	$53.85	$53.90
Purchase #3	$111.44	10.703%	$123.3674	$123.37	$123.35	$123.40
Purchase #4	$115.80	11.201%	$128.7708	$128.77	$128.75	$128.80
Purchase #5	$92.32	3.716%	$95.7506	$95.75	$95.75	$95.80
Purchase #6	$227.85	6.687%	$243.0863	$243.09	$243.10	$243.10
Purchase #7	$148.59	13.483%	$168.6244	$168.62	$168.60	$168.60
7 purchase totals =	$874.53		$954.2930	$954.30	$954.25	$954.40