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	$157.40	3.518%	$162.9373	$162.94	$162.95	$162.90
Purchase #2	$73.25	10.476%	$80.9237	$80.92	$80.90	$80.90
Purchase #3	$148.35	10.616%	$164.0988	$164.10	$164.10	$164.10
Purchase #4	$184.62	6.307%	$196.264	$196.26	$196.25	$196.30
Purchase #5	$59.96	5.521%	$63.2704	$63.27	$63.25	$63.30
Purchase #6	$108.77	9.327%	$118.915	$118.92	$118.90	$118.90
Purchase #7	$179.55	7.780%	$193.519	$193.52	$193.50	$193.50
7 purchase totals =	$911.90		$979.9282	$979.93	$979.85	$979.90