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	$79.54	13.501%	$90.2787	$90.28	$90.30	$90.30
Purchase #2	$172.44	12.743%	$194.414	$194.41	$194.40	$194.40
Purchase #3	$244.49	7.233%	$262.174	$262.17	$262.15	$262.20
Purchase #4	$209.95	3.788%	$217.9029	$217.90	$217.90	$217.90
Purchase #5	$74.46	9.384%	$81.4473	$81.45	$81.45	$81.40
Purchase #6	$23.32	3.347%	$24.1005	$24.10	$24.10	$24.10
Purchase #7	$140.92	3.767%	$146.2285	$146.23	$146.25	$146.20
7 purchase totals =	$945.12		$1,016.5459	$1,016.54	$1,016.55	$1,016.50