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	$151.93	10.133%	$167.3251	$167.33	$167.35	$167.30
Purchase #2	$42.53	13.609%	$48.3179	$48.32	$48.30	$48.30
Purchase #3	$244.67	11.327%	$272.3838	$272.38	$272.40	$272.40
Purchase #4	$11.66	12.839%	$13.157	$13.16	$13.15	$13.20
Purchase #5	$111.74	4.109%	$116.3314	$116.33	$116.35	$116.30
Purchase #6	$118.83	3.542%	$123.039	$123.04	$123.05	$123.00
Purchase #7	$181.57	5.839%	$192.1719	$192.17	$192.15	$192.20
7 purchase totals =	$862.93		$932.7261	$932.73	$932.75	$932.70