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	$163.96	5.307%	$172.6614	$172.66	$172.65	$172.70
Purchase #2	$96.89	13.447%	$109.9188	$109.92	$109.90	$109.90
Purchase #3	$90.68	11.182%	$100.8198	$100.82	$100.80	$100.80
Purchase #4	$29.27	5.834%	$30.9776	$30.98	$31.00	$31.00
Purchase #5	$190.57	11.378%	$212.2531	$212.25	$212.25	$212.30
Purchase #6	$60.78	8.276%	$65.8102	$65.81	$65.80	$65.80
Purchase #7	$128.95	3.406%	$133.342	$133.34	$133.35	$133.30
7 purchase totals =	$761.10		$825.7829	$825.78	$825.75	$825.80