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	$93.93	11.339%	$104.5807	$104.58	$104.60	$104.60
Purchase #2	$98.67	10.655%	$109.1833	$109.18	$109.20	$109.20
Purchase #3	$185.63	5.661%	$196.1385	$196.14	$196.15	$196.10
Purchase #4	$238.72	5.635%	$252.1719	$252.17	$252.15	$252.20
Purchase #5	$191.55	12.537%	$215.5646	$215.56	$215.55	$215.60
Purchase #6	$83.81	13.175%	$94.852	$94.85	$94.85	$94.90
Purchase #7	$138.64	11.721%	$154.89	$154.89	$154.90	$154.90
7 purchase totals =	$1,030.95		$1,127.3810	$1,127.37	$1,127.40	$1,127.50