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	$179.41	9.603%	$196.6387	$196.64	$196.65	$196.60
Purchase #2	$149.50	10.703%	$165.501	$165.50	$165.50	$165.50
Purchase #3	$143.26	9.775%	$157.2637	$157.26	$157.25	$157.30
Purchase #4	$137.34	8.436%	$148.926	$148.93	$148.95	$148.90
Purchase #5	$94.97	12.436%	$106.7805	$106.78	$106.80	$106.80
Purchase #6	$78.55	6.290%	$83.4908	$83.49	$83.50	$83.50
Purchase #7	$141.78	7.777%	$152.8062	$152.81	$152.80	$152.80
7 purchase totals =	$924.81		$1,011.4069	$1,011.41	$1,011.45	$1,011.40