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	$182.58	12.397%	$205.2144	$205.21	$205.20	$205.20
Purchase #2	$162.59	6.147%	$172.5844	$172.58	$172.60	$172.60
Purchase #3	$99.41	10.437%	$109.7854	$109.79	$109.80	$109.80
Purchase #4	$64.80	4.367%	$67.6298	$67.63	$67.65	$67.60
Purchase #5	$82.50	12.549%	$92.8529	$92.85	$92.85	$92.90
Purchase #6	$32.41	5.444%	$34.1744	$34.17	$34.15	$34.20
Purchase #7	$71.37	10.586%	$78.9252	$78.93	$78.95	$78.90
7 purchase totals =	$695.66		$761.1665	$761.16	$761.20	$761.20