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	$224.61	10.673%	$248.5826	$248.58	$248.60	$248.60
Purchase #2	$43.69	6.770%	$46.6478	$46.65	$46.65	$46.60
Purchase #3	$146.41	4.491%	$152.9853	$152.99	$153.00	$153.00
Purchase #4	$160.65	12.404%	$180.577	$180.58	$180.60	$180.60
Purchase #5	$188.53	4.372%	$196.7725	$196.77	$196.75	$196.80
Purchase #6	$33.63	13.345%	$38.1179	$38.12	$38.10	$38.10
Purchase #7	$194.42	12.234%	$218.2053	$218.21	$218.20	$218.20
7 purchase totals =	$991.94		$1,081.8884	$1,081.90	$1,081.90	$1,081.90