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	$191.86	7.107%	$205.4955	$205.50	$205.50	$205.50
Purchase #2	$21.65	5.461%	$22.8323	$22.83	$22.85	$22.80
Purchase #3	$112.58	5.680%	$118.9745	$118.97	$118.95	$119.00
Purchase #4	$40.60	12.867%	$45.824	$45.82	$45.80	$45.80
Purchase #5	$138.86	9.654%	$152.2655	$152.27	$152.25	$152.30
Purchase #6	$140.29	11.664%	$156.6534	$156.65	$156.65	$156.70
Purchase #7	$171.87	4.591%	$179.7606	$179.76	$179.75	$179.80
7 purchase totals =	$817.71		$881.8058	$881.80	$881.75	$881.90