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	$41.66	4.604%	$43.578	$43.58	$43.60	$43.60
Purchase #2	$35.37	11.619%	$39.4796	$39.48	$39.50	$39.50
Purchase #3	$166.92	7.544%	$179.5124	$179.51	$179.50	$179.50
Purchase #4	$77.55	7.156%	$83.0995	$83.10	$83.10	$83.10
Purchase #5	$92.81	11.308%	$103.305	$103.31	$103.30	$103.30
Purchase #6	$10.81	5.837%	$11.441	$11.44	$11.45	$11.40
Purchase #7	$85.83	9.486%	$93.9718	$93.97	$93.95	$94.00
7 purchase totals =	$510.95		$554.3873	$554.39	$554.40	$554.40