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	$208.84	12.740%	$235.4462	$235.45	$235.45	$235.40
Purchase #2	$233.35	4.822%	$244.6021	$244.60	$244.60	$244.60
Purchase #3	$27.80	4.553%	$29.0657	$29.07	$29.05	$29.10
Purchase #4	$33.35	13.613%	$37.8899	$37.89	$37.90	$37.90
Purchase #5	$211.52	11.543%	$235.9358	$235.94	$235.95	$235.90
Purchase #6	$41.57	5.645%	$43.9166	$43.92	$43.90	$43.90
Purchase #7	$145.97	7.163%	$156.4258	$156.43	$156.45	$156.40
7 purchase totals =	$902.40		$983.2821	$983.30	$983.30	$983.20