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	$109.38	3.348%	$113.042	$113.04	$113.05	$113.00
Purchase #2	$250.25	5.705%	$264.5268	$264.53	$264.55	$264.50
Purchase #3	$233.46	12.582%	$262.8339	$262.83	$262.85	$262.80
Purchase #4	$16.95	11.461%	$18.8926	$18.89	$18.90	$18.90
Purchase #5	$115.60	5.833%	$122.3429	$122.34	$122.35	$122.30
Purchase #6	$88.76	4.358%	$92.6282	$92.63	$92.65	$92.60
Purchase #7	$122.64	7.156%	$131.4161	$131.42	$131.40	$131.40
7 purchase totals =	$937.04		$1,005.6825	$1,005.68	$1,005.75	$1,005.50