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	$105.85	5.702%	$111.8856	$111.89	$111.90	$111.90
Purchase #2	$219.31	8.576%	$238.118	$238.12	$238.10	$238.10
Purchase #3	$215.29	8.472%	$233.5294	$233.53	$233.55	$233.50
Purchase #4	$148.72	12.215%	$166.8861	$166.89	$166.90	$166.90
Purchase #5	$153.69	4.428%	$160.4954	$160.50	$160.50	$160.50
Purchase #6	$36.62	7.180%	$39.2493	$39.25	$39.25	$39.20
Purchase #7	$205.60	3.689%	$213.1846	$213.18	$213.20	$213.20
7 purchase totals =	$1,085.08		$1,163.3484	$1,163.36	$1,163.40	$1,163.30