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	$143.70	4.660%	$150.3964	$150.40	$150.40	$150.40
Purchase #2	$85.67	6.396%	$91.1495	$91.15	$91.15	$91.10
Purchase #3	$219.81	6.864%	$234.8978	$234.90	$234.90	$234.90
Purchase #4	$249.30	9.157%	$272.1284	$272.13	$272.15	$272.10
Purchase #5	$59.35	12.280%	$66.6382	$66.64	$66.65	$66.60
Purchase #6	$77.59	3.839%	$80.5687	$80.57	$80.55	$80.60
Purchase #7	$34.86	6.859%	$37.251	$37.25	$37.25	$37.30
7 purchase totals =	$870.28		$933.0300	$933.04	$933.05	$933.00