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	$82.89	9.349%	$90.6394	$90.64	$90.65	$90.60
Purchase #2	$137.36	11.189%	$152.7292	$152.73	$152.75	$152.70
Purchase #3	$92.39	4.585%	$96.6261	$96.63	$96.65	$96.60
Purchase #4	$141.94	13.298%	$160.8152	$160.82	$160.80	$160.80
Purchase #5	$189.40	11.837%	$211.8193	$211.82	$211.80	$211.80
Purchase #6	$61.93	13.176%	$70.0899	$70.09	$70.10	$70.10
Purchase #7	$160.62	5.724%	$169.8139	$169.81	$169.80	$169.80
7 purchase totals =	$866.53		$952.5330	$952.54	$952.55	$952.40