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	$30.46	5.323%	$32.0814	$32.08	$32.10	$32.10
Purchase #2	$239.54	9.454%	$262.1861	$262.19	$262.20	$262.20
Purchase #3	$74.35	12.803%	$83.869	$83.87	$83.85	$83.90
Purchase #4	$63.54	6.837%	$67.8842	$67.88	$67.90	$67.90
Purchase #5	$198.88	11.870%	$222.4871	$222.49	$222.50	$222.50
Purchase #6	$216.47	4.614%	$226.4579	$226.46	$226.45	$226.50
Purchase #7	$178.75	6.601%	$190.5493	$190.55	$190.55	$190.50
7 purchase totals =	$1,001.99		$1,085.5150	$1,085.52	$1,085.55	$1,085.60