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	$231.39	3.123%	$238.6163	$238.62	$238.60	$238.60
Purchase #2	$189.60	4.686%	$198.4847	$198.48	$198.50	$198.50
Purchase #3	$50.84	13.669%	$57.7893	$57.79	$57.80	$57.80
Purchase #4	$153.81	12.335%	$172.7825	$172.78	$172.80	$172.80
Purchase #5	$190.56	7.566%	$204.9778	$204.98	$205.00	$205.00
Purchase #6	$69.25	11.442%	$77.1736	$77.17	$77.15	$77.20
Purchase #7	$182.82	7.264%	$196.1	$196.10	$196.10	$196.10
7 purchase totals =	$1,068.27		$1,145.9242	$1,145.92	$1,145.95	$1,146.00