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	$115.30	10.378%	$127.2658	$127.27	$127.25	$127.30
Purchase #2	$48.90	12.296%	$54.9127	$54.91	$54.90	$54.90
Purchase #3	$150.36	9.513%	$164.6637	$164.66	$164.65	$164.70
Purchase #4	$249.66	9.163%	$272.5363	$272.54	$272.55	$272.50
Purchase #5	$63.48	9.517%	$69.5214	$69.52	$69.50	$69.50
Purchase #6	$170.99	10.329%	$188.6516	$188.65	$188.65	$188.70
Purchase #7	$116.72	11.277%	$129.8825	$129.88	$129.90	$129.90
7 purchase totals =	$915.41		$1,007.4340	$1,007.43	$1,007.40	$1,007.50