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	$33.40	4.787%	$34.9989	$35.00	$35.00	$35.00
Purchase #2	$74.72	3.736%	$77.5115	$77.51	$77.50	$77.50
Purchase #3	$49.32	6.288%	$52.4212	$52.42	$52.40	$52.40
Purchase #4	$101.34	11.343%	$112.835	$112.84	$112.85	$112.80
Purchase #5	$197.51	3.198%	$203.8264	$203.83	$203.85	$203.80
Purchase #6	$118.84	4.160%	$123.7837	$123.78	$123.80	$123.80
Purchase #7	$80.50	6.142%	$85.4443	$85.44	$85.45	$85.40
7 purchase totals =	$655.63		$690.8210	$690.82	$690.85	$690.70