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	$132.93	7.587%	$143.0154	$143.02	$143.00	$143.00
Purchase #2	$49.40	6.540%	$52.6308	$52.63	$52.65	$52.60
Purchase #3	$247.81	13.337%	$280.8604	$280.86	$280.85	$280.90
Purchase #4	$200.60	10.725%	$222.1144	$222.11	$222.10	$222.10
Purchase #5	$68.38	7.402%	$73.4415	$73.44	$73.45	$73.40
Purchase #6	$167.91	9.864%	$184.4726	$184.47	$184.45	$184.50
Purchase #7	$113.41	6.569%	$120.8599	$120.86	$120.85	$120.90
7 purchase totals =	$980.44		$1,077.3950	$1,077.39	$1,077.35	$1,077.40