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	$67.48	6.269%	$71.7103	$71.71	$71.70	$71.70
Purchase #2	$149.49	5.196%	$157.2575	$157.26	$157.25	$157.30
Purchase #3	$204.50	12.684%	$230.4388	$230.44	$230.45	$230.40
Purchase #4	$166.73	5.453%	$175.8218	$175.82	$175.80	$175.80
Purchase #5	$247.69	13.236%	$280.4742	$280.47	$280.45	$280.50
Purchase #6	$70.60	3.152%	$72.8253	$72.83	$72.85	$72.80
Purchase #7	$92.71	5.713%	$98.0065	$98.01	$98.00	$98.00
7 purchase totals =	$999.20		$1,086.5344	$1,086.54	$1,086.50	$1,086.50