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	$203.94	13.790%	$232.0633	$232.06	$232.05	$232.10
Purchase #2	$54.48	8.544%	$59.1348	$59.13	$59.15	$59.10
Purchase #3	$30.37	3.724%	$31.501	$31.50	$31.50	$31.50
Purchase #4	$57.57	12.424%	$64.7225	$64.72	$64.70	$64.70
Purchase #5	$179.67	9.190%	$196.1817	$196.18	$196.20	$196.20
Purchase #6	$37.33	3.330%	$38.5731	$38.57	$38.55	$38.60
Purchase #7	$30.76	5.636%	$32.4936	$32.49	$32.50	$32.50
7 purchase totals =	$594.12		$654.6700	$654.65	$654.65	$654.70