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	$23.45	5.218%	$24.6736	$24.67	$24.65	$24.70
Purchase #2	$11.54	7.505%	$12.4061	$12.41	$12.40	$12.40
Purchase #3	$134.67	12.139%	$151.0176	$151.02	$151.00	$151.00
Purchase #4	$31.31	13.361%	$35.4933	$35.49	$35.50	$35.50
Purchase #5	$39.42	10.572%	$43.5875	$43.59	$43.60	$43.60
Purchase #6	$85.32	12.494%	$95.9799	$95.98	$96.00	$96.00
Purchase #7	$11.97	12.635%	$13.4824	$13.48	$13.50	$13.50
7 purchase totals =	$337.68		$376.6404	$376.64	$376.65	$376.70