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	$223.88	9.649%	$245.4822	$245.48	$245.50	$245.50
Purchase #2	$238.64	6.773%	$254.8031	$254.80	$254.80	$254.80
Purchase #3	$18.78	3.348%	$19.4088	$19.41	$19.40	$19.40
Purchase #4	$67.32	7.454%	$72.338	$72.34	$72.35	$72.30
Purchase #5	$31.91	8.521%	$34.6291	$34.63	$34.65	$34.60
Purchase #6	$18.44	10.864%	$20.4433	$20.44	$20.45	$20.40
Purchase #7	$62.86	4.750%	$65.8459	$65.85	$65.85	$65.80
7 purchase totals =	$661.83		$712.9504	$712.95	$713.00	$712.80