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	$81.80	3.832%	$84.9346	$84.93	$84.95	$84.90
Purchase #2	$89.30	3.661%	$92.5693	$92.57	$92.55	$92.60
Purchase #3	$6.80	11.273%	$7.5666	$7.57	$7.55	$7.60
Purchase #4	$24.52	13.751%	$27.8917	$27.89	$27.90	$27.90
Purchase #5	$148.44	8.199%	$160.6106	$160.61	$160.60	$160.60
Purchase #6	$135.52	6.727%	$144.6364	$144.64	$144.65	$144.60
Purchase #7	$164.90	4.651%	$172.5695	$172.57	$172.55	$172.60
7 purchase totals =	$651.28		$690.7787	$690.78	$690.75	$690.80