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	$115.50	13.606%	$131.2149	$131.21	$131.20	$131.20
Purchase #2	$162.85	7.795%	$175.5442	$175.54	$175.55	$175.50
Purchase #3	$178.79	10.150%	$196.9372	$196.94	$196.95	$196.90
Purchase #4	$188.73	12.123%	$211.6097	$211.61	$211.60	$211.60
Purchase #5	$139.35	3.509%	$144.2398	$144.24	$144.25	$144.20
Purchase #6	$136.57	7.748%	$147.1514	$147.15	$147.15	$147.20
Purchase #7	$116.58	11.416%	$129.8888	$129.89	$129.90	$129.90
7 purchase totals =	$1,038.37		$1,136.5860	$1,136.58	$1,136.60	$1,136.50