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	$155.94	7.831%	$168.1517	$168.15	$168.15	$168.20
Purchase #2	$114.29	11.608%	$127.5568	$127.56	$127.55	$127.60
Purchase #3	$43.71	12.403%	$49.1314	$49.13	$49.15	$49.10
Purchase #4	$64.37	10.753%	$71.2917	$71.29	$71.30	$71.30
Purchase #5	$201.40	5.746%	$212.9724	$212.97	$212.95	$213.00
Purchase #6	$205.86	3.219%	$212.4866	$212.49	$212.50	$212.50
Purchase #7	$116.44	6.138%	$123.5871	$123.59	$123.60	$123.60
7 purchase totals =	$902.01		$965.1777	$965.18	$965.20	$965.30