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	$30.65	7.215%	$32.8614	$32.86	$32.85	$32.90
Purchase #2	$80.36	4.529%	$83.9995	$84.00	$84.00	$84.00
Purchase #3	$196.35	7.606%	$211.2844	$211.28	$211.30	$211.30
Purchase #4	$240.69	4.673%	$251.9374	$251.94	$251.95	$251.90
Purchase #5	$176.75	3.864%	$183.5796	$183.58	$183.60	$183.60
Purchase #6	$113.72	8.590%	$123.4885	$123.49	$123.50	$123.50
Purchase #7	$144.42	8.635%	$156.8907	$156.89	$156.90	$156.90
7 purchase totals =	$982.94		$1,044.0415	$1,044.04	$1,044.10	$1,044.10