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	$215.31	3.555%	$222.9643	$222.96	$222.95	$223.00
Purchase #2	$242.52	6.134%	$257.3962	$257.40	$257.40	$257.40
Purchase #3	$155.74	11.284%	$173.3137	$173.31	$173.30	$173.30
Purchase #4	$97.36	11.833%	$108.8806	$108.88	$108.90	$108.90
Purchase #5	$207.68	7.469%	$223.1916	$223.19	$223.20	$223.20
Purchase #6	$106.45	9.804%	$116.8864	$116.89	$116.90	$116.90
Purchase #7	$32.88	13.824%	$37.4253	$37.43	$37.45	$37.40
7 purchase totals =	$1,057.94		$1,140.0581	$1,140.06	$1,140.10	$1,140.10