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	$182.98	13.732%	$208.1068	$208.11	$208.10	$208.10
Purchase #2	$80.98	12.155%	$90.8231	$90.82	$90.80	$90.80
Purchase #3	$93.78	3.717%	$97.2658	$97.27	$97.25	$97.30
Purchase #4	$160.86	6.663%	$171.5781	$171.58	$171.60	$171.60
Purchase #5	$183.46	11.162%	$203.9378	$203.94	$203.95	$203.90
Purchase #6	$232.91	3.640%	$241.3879	$241.39	$241.40	$241.40
Purchase #7	$238.66	4.542%	$249.4999	$249.50	$249.50	$249.50
7 purchase totals =	$1,173.63		$1,262.5994	$1,262.61	$1,262.60	$1,262.60