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	$224.43	8.642%	$243.8252	$243.83	$243.85	$243.80
Purchase #2	$35.56	7.407%	$38.1939	$38.19	$38.20	$38.20
Purchase #3	$11.50	13.176%	$13.0152	$13.02	$13.00	$13.00
Purchase #4	$174.52	7.243%	$187.1605	$187.16	$187.15	$187.20
Purchase #5	$73.76	6.563%	$78.6009	$78.60	$78.60	$78.60
Purchase #6	$210.40	3.235%	$217.2064	$217.21	$217.20	$217.20
Purchase #7	$164.48	5.142%	$172.9376	$172.94	$172.95	$172.90
7 purchase totals =	$894.65		$950.9397	$950.95	$950.95	$950.90