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	$126.94	9.613%	$139.1427	$139.14	$139.15	$139.10
Purchase #2	$66.82	7.523%	$71.8469	$71.85	$71.85	$71.80
Purchase #3	$246.82	9.356%	$269.9125	$269.91	$269.90	$269.90
Purchase #4	$203.70	8.745%	$221.5136	$221.51	$221.50	$221.50
Purchase #5	$147.55	6.102%	$156.5535	$156.55	$156.55	$156.60
Purchase #6	$37.82	10.643%	$41.8452	$41.85	$41.85	$41.80
Purchase #7	$105.39	4.767%	$110.4139	$110.41	$110.40	$110.40
7 purchase totals =	$935.04		$1,011.2283	$1,011.22	$1,011.20	$1,011.10