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	$133.71	3.504%	$138.3952	$138.40	$138.40	$138.40
Purchase #2	$134.63	7.845%	$145.1917	$145.19	$145.20	$145.20
Purchase #3	$11.44	10.152%	$12.6014	$12.60	$12.60	$12.60
Purchase #4	$162.31	10.825%	$179.8801	$179.88	$179.90	$179.90
Purchase #5	$233.38	11.129%	$259.3529	$259.35	$259.35	$259.40
Purchase #6	$134.35	12.553%	$151.215	$151.22	$151.20	$151.20
Purchase #7	$131.74	9.427%	$144.1591	$144.16	$144.15	$144.20
7 purchase totals =	$941.56		$1,030.7954	$1,030.80	$1,030.80	$1,030.90