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	$159.46	12.215%	$178.938	$178.94	$178.95	$178.90
Purchase #2	$153.29	4.558%	$160.277	$160.28	$160.30	$160.30
Purchase #3	$64.64	12.264%	$72.5674	$72.57	$72.55	$72.60
Purchase #4	$117.77	9.325%	$128.7521	$128.75	$128.75	$128.80
Purchase #5	$136.82	10.798%	$151.5938	$151.59	$151.60	$151.60
Purchase #6	$73.80	4.237%	$76.9269	$76.93	$76.95	$76.90
Purchase #7	$112.81	12.714%	$127.1527	$127.15	$127.15	$127.20
7 purchase totals =	$818.59		$896.2079	$896.21	$896.25	$896.30