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	$37.61	13.406%	$42.652	$42.65	$42.65	$42.70
Purchase #2	$152.87	6.156%	$162.2807	$162.28	$162.30	$162.30
Purchase #3	$39.41	3.189%	$40.6668	$40.67	$40.65	$40.70
Purchase #4	$178.47	3.275%	$184.3149	$184.31	$184.30	$184.30
Purchase #5	$209.41	4.782%	$219.424	$219.42	$219.40	$219.40
Purchase #6	$87.84	10.713%	$97.2503	$97.25	$97.25	$97.30
Purchase #7	$108.32	9.363%	$118.462	$118.46	$118.45	$118.50
7 purchase totals =	$813.93		$865.0507	$865.04	$865.00	$865.20