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	$200.37	5.615%	$211.6208	$211.62	$211.60	$211.60
Purchase #2	$138.44	3.186%	$142.8507	$142.85	$142.85	$142.90
Purchase #3	$198.34	10.695%	$219.5525	$219.55	$219.55	$219.60
Purchase #4	$134.66	6.124%	$142.9066	$142.91	$142.90	$142.90
Purchase #5	$41.45	6.777%	$44.2591	$44.26	$44.25	$44.30
Purchase #6	$146.83	3.167%	$151.4801	$151.48	$151.50	$151.50
Purchase #7	$230.37	9.264%	$251.7115	$251.71	$251.70	$251.70
7 purchase totals =	$1,090.46		$1,164.3813	$1,164.38	$1,164.35	$1,164.50