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	$117.25	11.856%	$131.1512	$131.15	$131.15	$131.20
Purchase #2	$93.30	3.263%	$96.3444	$96.34	$96.35	$96.30
Purchase #3	$241.59	12.751%	$272.3951	$272.40	$272.40	$272.40
Purchase #4	$70.45	9.519%	$77.1561	$77.16	$77.15	$77.20
Purchase #5	$58.96	6.121%	$62.5689	$62.57	$62.55	$62.60
Purchase #6	$119.28	7.196%	$127.8634	$127.86	$127.85	$127.90
Purchase #7	$171.65	4.587%	$179.5236	$179.52	$179.50	$179.50
7 purchase totals =	$872.48		$947.0027	$947.00	$946.95	$947.10