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	$116.32	9.500%	$127.3704	$127.37	$127.35	$127.40
Purchase #2	$214.79	7.302%	$230.474	$230.47	$230.45	$230.50
Purchase #3	$85.59	4.647%	$89.5674	$89.57	$89.55	$89.60
Purchase #4	$170.71	10.464%	$188.5731	$188.57	$188.55	$188.60
Purchase #5	$153.44	10.823%	$170.0468	$170.05	$170.05	$170.00
Purchase #6	$40.45	3.544%	$41.8835	$41.88	$41.90	$41.90
Purchase #7	$225.31	6.769%	$240.5612	$240.56	$240.55	$240.60
7 purchase totals =	$1,006.61		$1,088.4764	$1,088.47	$1,088.40	$1,088.60