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	$104.67	6.723%	$111.707	$111.71	$111.70	$111.70
Purchase #2	$24.94	9.780%	$27.3791	$27.38	$27.40	$27.40
Purchase #3	$188.85	6.302%	$200.7513	$200.75	$200.75	$200.80
Purchase #4	$146.42	12.372%	$164.5351	$164.54	$164.55	$164.50
Purchase #5	$7.35	6.350%	$7.8167	$7.82	$7.80	$7.80
Purchase #6	$133.67	7.430%	$143.6017	$143.60	$143.60	$143.60
Purchase #7	$94.64	5.395%	$99.7458	$99.75	$99.75	$99.70
7 purchase totals =	$700.54		$755.5367	$755.55	$755.55	$755.50