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	$168.56	13.323%	$191.0172	$191.02	$191.00	$191.00
Purchase #2	$28.66	9.211%	$31.2999	$31.30	$31.30	$31.30
Purchase #3	$13.41	5.463%	$14.1426	$14.14	$14.15	$14.10
Purchase #4	$102.87	10.691%	$113.8678	$113.87	$113.85	$113.90
Purchase #5	$111.38	13.464%	$126.3762	$126.38	$126.40	$126.40
Purchase #6	$187.30	4.678%	$196.0619	$196.06	$196.05	$196.10
Purchase #7	$95.59	10.830%	$105.9424	$105.94	$105.95	$105.90
7 purchase totals =	$707.77		$778.7080	$778.71	$778.70	$778.70