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	$64.97	13.554%	$73.776	$73.78	$73.80	$73.80
Purchase #2	$107.61	7.342%	$115.5107	$115.51	$115.50	$115.50
Purchase #3	$140.37	7.852%	$151.3919	$151.39	$151.40	$151.40
Purchase #4	$47.43	4.525%	$49.5762	$49.58	$49.60	$49.60
Purchase #5	$237.64	4.210%	$247.6446	$247.64	$247.65	$247.60
Purchase #6	$31.89	7.621%	$34.3203	$34.32	$34.30	$34.30
Purchase #7	$78.76	13.171%	$89.1335	$89.13	$89.15	$89.10
7 purchase totals =	$708.67		$761.3532	$761.35	$761.40	$761.30