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	$34.27	3.195%	$35.3649	$35.36	$35.35	$35.40
Purchase #2	$177.63	3.152%	$183.2289	$183.23	$183.25	$183.20
Purchase #3	$90.50	7.364%	$97.1644	$97.16	$97.15	$97.20
Purchase #4	$131.59	10.489%	$145.3925	$145.39	$145.40	$145.40
Purchase #5	$108.83	3.667%	$112.8208	$112.82	$112.80	$112.80
Purchase #6	$127.32	4.768%	$133.3906	$133.39	$133.40	$133.40
Purchase #7	$130.93	6.476%	$139.409	$139.41	$139.40	$139.40
7 purchase totals =	$801.07		$846.7711	$846.76	$846.75	$846.80