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	$181.47	5.504%	$191.4581	$191.46	$191.45	$191.50
Purchase #2	$240.50	7.669%	$258.9439	$258.94	$258.95	$258.90
Purchase #3	$141.31	8.409%	$153.1928	$153.19	$153.20	$153.20
Purchase #4	$93.51	12.674%	$105.3615	$105.36	$105.35	$105.40
Purchase #5	$109.41	6.444%	$116.4604	$116.46	$116.45	$116.50
Purchase #6	$56.94	4.377%	$59.4323	$59.43	$59.45	$59.40
Purchase #7	$196.57	8.851%	$213.9684	$213.97	$213.95	$214.00
7 purchase totals =	$1,019.71		$1,098.8174	$1,098.81	$1,098.80	$1,098.90