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	$123.94	13.860%	$141.1181	$141.12	$141.10	$141.10
Purchase #2	$22.86	4.800%	$23.9573	$23.96	$23.95	$24.00
Purchase #3	$77.29	13.144%	$87.449	$87.45	$87.45	$87.40
Purchase #4	$208.92	9.107%	$227.9463	$227.95	$227.95	$227.90
Purchase #5	$155.41	10.604%	$171.8897	$171.89	$171.90	$171.90
Purchase #6	$221.85	5.311%	$233.6325	$233.63	$233.65	$233.60
Purchase #7	$183.83	3.423%	$190.1225	$190.12	$190.10	$190.10
7 purchase totals =	$994.10		$1,076.1154	$1,076.12	$1,076.10	$1,076.00