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	$143.49	10.303%	$158.2738	$158.27	$158.25	$158.30
Purchase #2	$20.90	8.628%	$22.7033	$22.70	$22.70	$22.70
Purchase #3	$173.78	10.551%	$192.1155	$192.12	$192.10	$192.10
Purchase #4	$123.87	3.725%	$128.4842	$128.48	$128.50	$128.50
Purchase #5	$209.98	11.634%	$234.4091	$234.41	$234.40	$234.40
Purchase #6	$208.31	3.269%	$215.1197	$215.12	$215.10	$215.10
Purchase #7	$30.55	6.234%	$32.4545	$32.45	$32.45	$32.50
7 purchase totals =	$910.88		$983.5601	$983.55	$983.50	$983.60