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	$167.66	7.169%	$179.6795	$179.68	$179.70	$179.70
Purchase #2	$127.32	10.345%	$140.4913	$140.49	$140.50	$140.50
Purchase #3	$78.30	11.520%	$87.3202	$87.32	$87.30	$87.30
Purchase #4	$51.90	5.740%	$54.8791	$54.88	$54.90	$54.90
Purchase #5	$230.29	8.815%	$250.5901	$250.59	$250.60	$250.60
Purchase #6	$115.90	6.715%	$123.6827	$123.68	$123.70	$123.70
Purchase #7	$214.26	3.615%	$222.0055	$222.01	$222.00	$222.00
7 purchase totals =	$985.63		$1,058.6484	$1,058.65	$1,058.70	$1,058.70