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	$157.41	4.797%	$164.961	$164.96	$164.95	$165.00
Purchase #2	$136.34	5.579%	$143.9464	$143.95	$143.95	$143.90
Purchase #3	$202.81	11.850%	$226.843	$226.84	$226.85	$226.80
Purchase #4	$115.94	6.142%	$123.061	$123.06	$123.05	$123.10
Purchase #5	$230.48	3.613%	$238.8072	$238.81	$238.80	$238.80
Purchase #6	$78.27	5.447%	$82.5334	$82.53	$82.55	$82.50
Purchase #7	$60.64	5.166%	$63.7727	$63.77	$63.75	$63.80
7 purchase totals =	$981.89		$1,043.9247	$1,043.92	$1,043.90	$1,043.90