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	$193.75	3.450%	$200.4344	$200.43	$200.45	$200.40
Purchase #2	$78.57	3.737%	$81.5062	$81.51	$81.50	$81.50
Purchase #3	$133.87	4.215%	$139.5126	$139.51	$139.50	$139.50
Purchase #4	$143.45	3.190%	$148.0261	$148.03	$148.05	$148.00
Purchase #5	$90.38	11.332%	$100.6219	$100.62	$100.60	$100.60
Purchase #6	$191.36	10.575%	$211.5963	$211.60	$211.60	$211.60
Purchase #7	$198.89	11.224%	$221.2134	$221.21	$221.20	$221.20
7 purchase totals =	$1,030.27		$1,102.9109	$1,102.91	$1,102.90	$1,102.80