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	$212.83	9.720%	$233.5171	$233.52	$233.50	$233.50
Purchase #2	$12.66	7.460%	$13.6044	$13.60	$13.60	$13.60
Purchase #3	$12.85	6.782%	$13.7215	$13.72	$13.70	$13.70
Purchase #4	$235.31	7.527%	$253.0218	$253.02	$253.00	$253.00
Purchase #5	$33.95	8.569%	$36.8592	$36.86	$36.85	$36.90
Purchase #6	$74.68	11.252%	$83.083	$83.08	$83.10	$83.10
Purchase #7	$13.85	4.765%	$14.51	$14.51	$14.50	$14.50
7 purchase totals =	$596.13		$648.3170	$648.31	$648.25	$648.30