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	$72.89	6.475%	$77.6096	$77.61	$77.60	$77.60
Purchase #2	$209.50	9.597%	$229.6057	$229.61	$229.60	$229.60
Purchase #3	$248.43	5.228%	$261.4179	$261.42	$261.40	$261.40
Purchase #4	$206.98	9.778%	$227.2185	$227.22	$227.20	$227.20
Purchase #5	$72.46	6.510%	$77.1771	$77.18	$77.20	$77.20
Purchase #6	$42.77	4.262%	$44.5929	$44.59	$44.60	$44.60
Purchase #7	$128.65	12.113%	$144.2334	$144.23	$144.25	$144.20
7 purchase totals =	$981.68		$1,061.8551	$1,061.86	$1,061.85	$1,061.80