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	$156.26	10.664%	$172.9236	$172.92	$172.90	$172.90
Purchase #2	$197.32	10.112%	$217.273	$217.27	$217.25	$217.30
Purchase #3	$66.51	8.510%	$72.17	$72.17	$72.15	$72.20
Purchase #4	$56.68	9.223%	$61.9076	$61.91	$61.90	$61.90
Purchase #5	$41.58	5.484%	$43.8602	$43.86	$43.85	$43.90
Purchase #6	$192.96	7.817%	$208.0437	$208.04	$208.05	$208.00
Purchase #7	$236.98	11.231%	$263.5952	$263.60	$263.60	$263.60
7 purchase totals =	$948.29		$1,039.7733	$1,039.77	$1,039.70	$1,039.80