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	$115.91	9.225%	$126.6027	$126.60	$126.60	$126.60
Purchase #2	$121.81	7.175%	$130.5499	$130.55	$130.55	$130.50
Purchase #3	$102.59	9.518%	$112.3545	$112.35	$112.35	$112.40
Purchase #4	$232.78	10.384%	$256.9519	$256.95	$256.95	$257.00
Purchase #5	$187.68	12.731%	$211.5735	$211.57	$211.55	$211.60
Purchase #6	$80.71	12.386%	$90.7067	$90.71	$90.70	$90.70
Purchase #7	$158.35	9.146%	$172.8327	$172.83	$172.85	$172.80
7 purchase totals =	$999.83		$1,101.5719	$1,101.56	$1,101.55	$1,101.60