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	$104.49	13.763%	$118.871	$118.87	$118.85	$118.90
Purchase #2	$160.26	13.585%	$182.0313	$182.03	$182.05	$182.00
Purchase #3	$166.89	7.132%	$178.7926	$178.79	$178.80	$178.80
Purchase #4	$48.92	5.161%	$51.4448	$51.44	$51.45	$51.40
Purchase #5	$130.70	8.139%	$141.3377	$141.34	$141.35	$141.30
Purchase #6	$55.54	6.683%	$59.2517	$59.25	$59.25	$59.30
Purchase #7	$128.48	11.768%	$143.5995	$143.60	$143.60	$143.60
7 purchase totals =	$795.28		$875.3286	$875.32	$875.35	$875.30