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	$61.57	3.167%	$63.5199	$63.52	$63.50	$63.50
Purchase #2	$9.76	10.765%	$10.8107	$10.81	$10.80	$10.80
Purchase #3	$99.86	3.231%	$103.0865	$103.09	$103.10	$103.10
Purchase #4	$170.51	12.783%	$192.3063	$192.31	$192.30	$192.30
Purchase #5	$67.49	4.354%	$70.4285	$70.43	$70.45	$70.40
Purchase #6	$144.76	13.784%	$164.7137	$164.71	$164.70	$164.70
Purchase #7	$63.91	13.168%	$72.3257	$72.33	$72.35	$72.30
7 purchase totals =	$617.86		$677.1913	$677.20	$677.20	$677.10