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	$145.99	7.484%	$156.9159	$156.92	$156.90	$156.90
Purchase #2	$72.32	8.800%	$78.6842	$78.68	$78.70	$78.70
Purchase #3	$97.96	13.412%	$111.0984	$111.10	$111.10	$111.10
Purchase #4	$100.31	6.331%	$106.6606	$106.66	$106.65	$106.70
Purchase #5	$32.68	5.290%	$34.4088	$34.41	$34.40	$34.40
Purchase #6	$249.95	4.846%	$262.0626	$262.06	$262.05	$262.10
Purchase #7	$38.67	11.530%	$43.1287	$43.13	$43.15	$43.10
7 purchase totals =	$737.88		$792.9592	$792.96	$792.95	$793.00