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	$53.45	11.475%	$59.5834	$59.58	$59.60	$59.60
Purchase #2	$242.30	6.723%	$258.5898	$258.59	$258.60	$258.60
Purchase #3	$171.50	11.155%	$190.6308	$190.63	$190.65	$190.60
Purchase #4	$117.40	12.655%	$132.257	$132.26	$132.25	$132.30
Purchase #5	$51.80	3.539%	$53.6332	$53.63	$53.65	$53.60
Purchase #6	$161.54	5.684%	$170.7219	$170.72	$170.70	$170.70
Purchase #7	$237.95	13.132%	$269.1976	$269.20	$269.20	$269.20
7 purchase totals =	$1,035.94		$1,134.6137	$1,134.61	$1,134.65	$1,134.60