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	$244.35	7.150%	$261.821	$261.82	$261.80	$261.80
Purchase #2	$196.39	4.640%	$205.5025	$205.50	$205.50	$205.50
Purchase #3	$28.67	8.795%	$31.1915	$31.19	$31.20	$31.20
Purchase #4	$116.52	9.195%	$127.234	$127.23	$127.25	$127.20
Purchase #5	$178.45	9.534%	$195.4634	$195.46	$195.45	$195.50
Purchase #6	$196.97	10.759%	$218.162	$218.16	$218.15	$218.20
Purchase #7	$139.43	10.521%	$154.0994	$154.10	$154.10	$154.10
7 purchase totals =	$1,100.78		$1,193.4738	$1,193.46	$1,193.45	$1,193.50