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	$32.73	3.787%	$33.9695	$33.97	$33.95	$34.00
Purchase #2	$12.52	4.842%	$13.1262	$13.13	$13.15	$13.10
Purchase #3	$237.85	8.271%	$257.5226	$257.52	$257.50	$257.50
Purchase #4	$230.94	4.321%	$240.9189	$240.92	$240.90	$240.90
Purchase #5	$36.80	6.751%	$39.2844	$39.28	$39.30	$39.30
Purchase #6	$173.33	5.513%	$182.8857	$182.89	$182.90	$182.90
Purchase #7	$227.33	10.557%	$251.3292	$251.33	$251.35	$251.30
7 purchase totals =	$951.50		$1,019.0365	$1,019.04	$1,019.05	$1,019.00