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	$192.28	11.731%	$214.8364	$214.84	$214.85	$214.80
Purchase #2	$133.71	4.580%	$139.8339	$139.83	$139.85	$139.80
Purchase #3	$50.65	3.851%	$52.6005	$52.60	$52.60	$52.60
Purchase #4	$29.67	10.437%	$32.7667	$32.77	$32.75	$32.80
Purchase #5	$18.50	10.216%	$20.39	$20.39	$20.40	$20.40
Purchase #6	$118.63	4.175%	$123.5828	$123.58	$123.60	$123.60
Purchase #7	$118.36	9.743%	$129.8918	$129.89	$129.90	$129.90
7 purchase totals =	$661.80		$713.9021	$713.90	$713.95	$713.90