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	$99.86	11.524%	$111.3679	$111.37	$111.35	$111.40
Purchase #2	$118.48	9.597%	$129.8505	$129.85	$129.85	$129.90
Purchase #3	$56.89	8.567%	$61.7638	$61.76	$61.75	$61.80
Purchase #4	$82.84	12.795%	$93.4394	$93.44	$93.45	$93.40
Purchase #5	$234.78	11.833%	$262.5615	$262.56	$262.55	$262.60
Purchase #6	$236.40	10.789%	$261.9052	$261.91	$261.90	$261.90
Purchase #7	$76.77	12.132%	$86.0837	$86.08	$86.10	$86.10
7 purchase totals =	$906.02		$1,006.9720	$1,006.97	$1,006.95	$1,007.10