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	$202.40	4.209%	$210.919	$210.92	$210.90	$210.90
Purchase #2	$97.68	5.320%	$102.8766	$102.88	$102.90	$102.90
Purchase #3	$36.40	4.352%	$37.9841	$37.98	$38.00	$38.00
Purchase #4	$135.27	4.548%	$141.4221	$141.42	$141.40	$141.40
Purchase #5	$137.80	13.577%	$156.5091	$156.51	$156.50	$156.50
Purchase #6	$176.31	5.217%	$185.5081	$185.51	$185.50	$185.50
Purchase #7	$54.70	9.698%	$60.0048	$60.00	$60.00	$60.00
7 purchase totals =	$840.56		$895.2238	$895.22	$895.20	$895.20