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	$41.38	5.388%	$43.6096	$43.61	$43.60	$43.60
Purchase #2	$82.61	7.862%	$89.1048	$89.10	$89.10	$89.10
Purchase #3	$224.38	4.287%	$233.9992	$234.00	$234.00	$234.00
Purchase #4	$56.40	11.638%	$62.9638	$62.96	$62.95	$63.00
Purchase #5	$38.40	5.581%	$40.5431	$40.54	$40.55	$40.50
Purchase #6	$124.74	4.230%	$130.0165	$130.02	$130.00	$130.00
Purchase #7	$217.26	13.606%	$246.8204	$246.82	$246.80	$246.80
7 purchase totals =	$785.17		$847.0574	$847.05	$847.00	$847.00