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	$59.98	8.454%	$65.0507	$65.05	$65.05	$65.10
Purchase #2	$112.90	13.587%	$128.2397	$128.24	$128.25	$128.20
Purchase #3	$69.99	9.311%	$76.5068	$76.51	$76.50	$76.50
Purchase #4	$113.48	13.331%	$128.608	$128.61	$128.60	$128.60
Purchase #5	$51.29	12.615%	$57.7602	$57.76	$57.75	$57.80
Purchase #6	$147.29	6.536%	$156.9169	$156.92	$156.90	$156.90
Purchase #7	$39.41	4.850%	$41.3214	$41.32	$41.30	$41.30
7 purchase totals =	$594.34		$654.4037	$654.41	$654.35	$654.40