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	$167.54	11.787%	$187.2879	$187.29	$187.30	$187.30
Purchase #2	$228.48	11.620%	$255.0294	$255.03	$255.05	$255.00
Purchase #3	$160.30	13.832%	$182.4727	$182.47	$182.45	$182.50
Purchase #4	$52.69	8.335%	$57.0817	$57.08	$57.10	$57.10
Purchase #5	$102.51	10.417%	$113.1885	$113.19	$113.20	$113.20
Purchase #6	$160.35	7.591%	$172.5222	$172.52	$172.50	$172.50
Purchase #7	$178.27	5.352%	$187.811	$187.81	$187.80	$187.80
7 purchase totals =	$1,050.14		$1,155.3934	$1,155.39	$1,155.40	$1,155.40