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	$174.89	13.444%	$198.4022	$198.40	$198.40	$198.40
Purchase #2	$38.50	9.770%	$42.2615	$42.26	$42.25	$42.30
Purchase #3	$194.79	7.205%	$208.8246	$208.82	$208.80	$208.80
Purchase #4	$77.58	5.819%	$82.0944	$82.09	$82.10	$82.10
Purchase #5	$201.65	7.801%	$217.3807	$217.38	$217.40	$217.40
Purchase #6	$205.63	11.311%	$228.8888	$228.89	$228.90	$228.90
Purchase #7	$95.36	4.460%	$99.6131	$99.61	$99.60	$99.60
7 purchase totals =	$988.40		$1,077.4653	$1,077.45	$1,077.45	$1,077.50