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	$39.98	13.204%	$45.259	$45.26	$45.25	$45.30
Purchase #2	$90.34	7.210%	$96.8535	$96.85	$96.85	$96.90
Purchase #3	$45.49	5.149%	$47.8323	$47.83	$47.85	$47.80
Purchase #4	$165.89	6.624%	$176.8786	$176.88	$176.90	$176.90
Purchase #5	$80.69	7.295%	$86.5763	$86.58	$86.60	$86.60
Purchase #6	$223.42	6.463%	$237.8596	$237.86	$237.85	$237.90
Purchase #7	$186.93	12.604%	$210.4907	$210.49	$210.50	$210.50
7 purchase totals =	$832.74		$901.7500	$901.75	$901.80	$901.90