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	$10.56	10.738%	$11.6939	$11.69	$11.70	$11.70
Purchase #2	$132.81	8.474%	$144.0643	$144.06	$144.05	$144.10
Purchase #3	$127.89	8.312%	$138.5202	$138.52	$138.50	$138.50
Purchase #4	$240.93	6.643%	$256.935	$256.94	$256.95	$256.90
Purchase #5	$46.81	13.728%	$53.2361	$53.24	$53.25	$53.20
Purchase #6	$38.92	8.180%	$42.1037	$42.10	$42.10	$42.10
Purchase #7	$155.88	8.369%	$168.9256	$168.93	$168.95	$168.90
7 purchase totals =	$753.80		$815.4788	$815.48	$815.50	$815.40