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	$215.59	3.709%	$223.5862	$223.59	$223.60	$223.60
Purchase #2	$151.45	6.105%	$160.696	$160.70	$160.70	$160.70
Purchase #3	$197.93	6.569%	$210.932	$210.93	$210.95	$210.90
Purchase #4	$112.63	3.473%	$116.5416	$116.54	$116.55	$116.50
Purchase #5	$222.82	6.863%	$238.1121	$238.11	$238.10	$238.10
Purchase #6	$207.32	7.578%	$223.0307	$223.03	$223.05	$223.00
Purchase #7	$77.95	5.186%	$81.9925	$81.99	$82.00	$82.00
7 purchase totals =	$1,185.69		$1,254.8911	$1,254.89	$1,254.95	$1,254.80