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	$210.28	5.336%	$221.5005	$221.50	$221.50	$221.50
Purchase #2	$147.94	10.659%	$163.7089	$163.71	$163.70	$163.70
Purchase #3	$168.64	4.630%	$176.448	$176.45	$176.45	$176.40
Purchase #4	$219.83	3.350%	$227.1943	$227.19	$227.20	$227.20
Purchase #5	$211.59	5.625%	$223.4919	$223.49	$223.50	$223.50
Purchase #6	$56.92	4.249%	$59.3385	$59.34	$59.35	$59.30
Purchase #7	$69.60	12.787%	$78.4998	$78.50	$78.50	$78.50
7 purchase totals =	$1,084.80		$1,150.1819	$1,150.18	$1,150.20	$1,150.10