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	$157.51	5.352%	$165.9399	$165.94	$165.95	$165.90
Purchase #2	$179.84	9.507%	$196.9374	$196.94	$196.95	$196.90
Purchase #3	$29.92	11.606%	$33.3925	$33.39	$33.40	$33.40
Purchase #4	$146.45	7.158%	$156.9329	$156.93	$156.95	$156.90
Purchase #5	$120.51	13.284%	$136.5185	$136.52	$136.50	$136.50
Purchase #6	$59.99	5.771%	$63.452	$63.45	$63.45	$63.50
Purchase #7	$124.68	10.618%	$137.9185	$137.92	$137.90	$137.90
7 purchase totals =	$818.90		$891.0917	$891.09	$891.10	$891.00