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	$168.75	10.377%	$186.2612	$186.26	$186.25	$186.30
Purchase #2	$113.52	11.477%	$126.5487	$126.55	$126.55	$126.50
Purchase #3	$40.78	8.558%	$44.27	$44.27	$44.25	$44.30
Purchase #4	$172.65	5.107%	$181.4672	$181.47	$181.45	$181.50
Purchase #5	$18.83	13.392%	$21.3517	$21.35	$21.35	$21.40
Purchase #6	$144.65	4.841%	$151.6525	$151.65	$151.65	$151.70
Purchase #7	$39.97	8.547%	$43.3862	$43.39	$43.40	$43.40
7 purchase totals =	$699.15		$754.9375	$754.94	$754.90	$755.10