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	$151.57	5.806%	$160.3702	$160.37	$160.35	$160.40
Purchase #2	$59.76	5.866%	$63.2655	$63.27	$63.25	$63.30
Purchase #3	$162.53	9.797%	$178.4531	$178.45	$178.45	$178.50
Purchase #4	$246.25	4.839%	$258.166	$258.17	$258.15	$258.20
Purchase #5	$80.42	12.756%	$90.6784	$90.68	$90.70	$90.70
Purchase #6	$197.47	11.312%	$219.8078	$219.81	$219.80	$219.80
Purchase #7	$33.76	13.132%	$38.1934	$38.19	$38.20	$38.20
7 purchase totals =	$931.76		$1,008.9344	$1,008.94	$1,008.90	$1,009.10