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	$189.82	8.162%	$205.3131	$205.31	$205.30	$205.30
Purchase #2	$34.31	4.531%	$35.8646	$35.86	$35.85	$35.90
Purchase #3	$249.65	12.450%	$280.7314	$280.73	$280.75	$280.70
Purchase #4	$46.63	6.442%	$49.6339	$49.63	$49.65	$49.60
Purchase #5	$250.89	10.643%	$277.5922	$277.59	$277.60	$277.60
Purchase #6	$38.47	13.340%	$43.6019	$43.60	$43.60	$43.60
Purchase #7	$152.57	6.291%	$162.1682	$162.17	$162.15	$162.20
7 purchase totals =	$962.34		$1,054.9053	$1,054.89	$1,054.90	$1,054.90