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	$182.48	7.646%	$196.4324	$196.43	$196.45	$196.40
Purchase #2	$89.49	11.605%	$99.8753	$99.88	$99.90	$99.90
Purchase #3	$70.43	9.406%	$77.0546	$77.05	$77.05	$77.10
Purchase #4	$27.27	6.439%	$29.0259	$29.03	$29.05	$29.00
Purchase #5	$170.51	5.483%	$179.8591	$179.86	$179.85	$179.90
Purchase #6	$205.29	4.592%	$214.7169	$214.72	$214.70	$214.70
Purchase #7	$107.40	10.217%	$118.3731	$118.37	$118.35	$118.40
7 purchase totals =	$852.87		$915.3373	$915.34	$915.35	$915.40