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	$168.48	4.646%	$176.3076	$176.31	$176.30	$176.30
Purchase #2	$184.72	6.634%	$196.9743	$196.97	$196.95	$197.00
Purchase #3	$81.58	12.437%	$91.7261	$91.73	$91.75	$91.70
Purchase #4	$96.98	13.320%	$109.8977	$109.90	$109.90	$109.90
Purchase #5	$241.71	13.149%	$273.4924	$273.49	$273.50	$273.50
Purchase #6	$154.25	5.690%	$163.0268	$163.03	$163.05	$163.00
Purchase #7	$105.79	6.337%	$112.4939	$112.49	$112.50	$112.50
7 purchase totals =	$1,033.51		$1,123.9188	$1,123.92	$1,123.95	$1,123.90