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	$88.95	13.860%	$101.2785	$101.28	$101.30	$101.30
Purchase #2	$110.84	13.164%	$125.431	$125.43	$125.45	$125.40
Purchase #3	$118.57	6.453%	$126.2213	$126.22	$126.20	$126.20
Purchase #4	$233.85	3.229%	$241.401	$241.40	$241.40	$241.40
Purchase #5	$86.65	4.312%	$90.3863	$90.39	$90.40	$90.40
Purchase #6	$176.27	3.707%	$182.8043	$182.80	$182.80	$182.80
Purchase #7	$113.82	8.822%	$123.8612	$123.86	$123.85	$123.90
7 purchase totals =	$928.95		$991.3836	$991.38	$991.40	$991.40