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	$86.59	4.255%	$90.2744	$90.27	$90.25	$90.30
Purchase #2	$19.59	4.293%	$20.431	$20.43	$20.45	$20.40
Purchase #3	$200.77	6.291%	$213.4004	$213.40	$213.40	$213.40
Purchase #4	$29.43	9.704%	$32.2859	$32.29	$32.30	$32.30
Purchase #5	$100.65	9.401%	$110.1121	$110.11	$110.10	$110.10
Purchase #6	$242.94	11.174%	$270.0861	$270.09	$270.10	$270.10
Purchase #7	$180.81	12.534%	$203.4727	$203.47	$203.45	$203.50
7 purchase totals =	$860.78		$940.0626	$940.06	$940.05	$940.10