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	$62.31	4.396%	$65.0491	$65.05	$65.05	$65.00
Purchase #2	$115.61	13.470%	$131.1827	$131.18	$131.20	$131.20
Purchase #3	$106.32	8.604%	$115.4678	$115.47	$115.45	$115.50
Purchase #4	$32.89	10.858%	$36.4612	$36.46	$36.45	$36.50
Purchase #5	$151.80	7.139%	$162.637	$162.64	$162.65	$162.60
Purchase #6	$118.98	11.117%	$132.207	$132.21	$132.20	$132.20
Purchase #7	$95.26	11.159%	$105.8901	$105.89	$105.90	$105.90
7 purchase totals =	$683.17		$748.8949	$748.90	$748.90	$748.90