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	$202.63	5.103%	$212.9702	$212.97	$212.95	$213.00
Purchase #2	$13.89	9.229%	$15.1719	$15.17	$15.15	$15.20
Purchase #3	$239.46	12.491%	$269.3709	$269.37	$269.35	$269.40
Purchase #4	$76.88	4.823%	$80.5879	$80.59	$80.60	$80.60
Purchase #5	$201.56	11.106%	$223.9453	$223.95	$223.95	$223.90
Purchase #6	$213.39	4.461%	$222.9093	$222.91	$222.90	$222.90
Purchase #7	$63.98	10.225%	$70.522	$70.52	$70.50	$70.50
7 purchase totals =	$1,011.79		$1,095.4775	$1,095.48	$1,095.40	$1,095.50