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	$9.89	9.720%	$10.8513	$10.85	$10.85	$10.90
Purchase #2	$18.71	9.611%	$20.5082	$20.51	$20.50	$20.50
Purchase #3	$240.39	6.502%	$256.0202	$256.02	$256.00	$256.00
Purchase #4	$190.28	9.255%	$207.8904	$207.89	$207.90	$207.90
Purchase #5	$29.32	5.785%	$31.0162	$31.02	$31.00	$31.00
Purchase #6	$106.64	4.473%	$111.41	$111.41	$111.40	$111.40
Purchase #7	$159.46	5.793%	$168.6975	$168.70	$168.70	$168.70
7 purchase totals =	$754.69		$806.3938	$806.40	$806.35	$806.40