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	$228.66	7.587%	$246.0084	$246.01	$246.00	$246.00
Purchase #2	$168.69	8.450%	$182.9443	$182.94	$182.95	$182.90
Purchase #3	$138.26	3.308%	$142.8336	$142.83	$142.85	$142.80
Purchase #4	$52.69	12.544%	$59.2994	$59.30	$59.30	$59.30
Purchase #5	$129.59	9.613%	$142.0475	$142.05	$142.05	$142.00
Purchase #6	$59.90	3.382%	$61.9258	$61.93	$61.95	$61.90
Purchase #7	$48.93	6.513%	$52.1168	$52.12	$52.10	$52.10
7 purchase totals =	$826.72		$887.1758	$887.18	$887.20	$887.00