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	$140.85	9.838%	$154.7068	$154.71	$154.70	$154.70
Purchase #2	$214.77	13.576%	$243.9272	$243.93	$243.95	$243.90
Purchase #3	$190.63	6.825%	$203.6405	$203.64	$203.65	$203.60
Purchase #4	$54.50	9.168%	$59.4966	$59.50	$59.50	$59.50
Purchase #5	$225.65	13.754%	$256.6859	$256.69	$256.70	$256.70
Purchase #6	$57.77	12.827%	$65.1802	$65.18	$65.20	$65.20
Purchase #7	$33.39	8.555%	$36.2465	$36.25	$36.25	$36.20
7 purchase totals =	$917.56		$1,019.8837	$1,019.90	$1,019.95	$1,019.80