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	$41.68	8.442%	$45.1986	$45.20	$45.20	$45.20
Purchase #2	$25.28	8.561%	$27.4442	$27.44	$27.45	$27.40
Purchase #3	$119.73	6.476%	$127.4837	$127.48	$127.50	$127.50
Purchase #4	$52.37	8.605%	$56.8764	$56.88	$56.90	$56.90
Purchase #5	$16.48	6.801%	$17.6008	$17.60	$17.60	$17.60
Purchase #6	$124.63	5.492%	$131.4747	$131.47	$131.45	$131.50
Purchase #7	$116.77	11.427%	$130.1133	$130.11	$130.10	$130.10
7 purchase totals =	$496.94		$536.1917	$536.18	$536.20	$536.20