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	$239.89	4.742%	$251.2656	$251.27	$251.25	$251.30
Purchase #2	$205.85	6.318%	$218.8556	$218.86	$218.85	$218.90
Purchase #3	$141.27	6.620%	$150.6221	$150.62	$150.60	$150.60
Purchase #4	$42.27	9.693%	$46.3672	$46.37	$46.35	$46.40
Purchase #5	$102.28	13.311%	$115.8945	$115.89	$115.90	$115.90
Purchase #6	$235.47	7.509%	$253.1514	$253.15	$253.15	$253.20
Purchase #7	$57.27	8.192%	$61.9616	$61.96	$61.95	$62.00
7 purchase totals =	$1,024.30		$1,098.1180	$1,098.12	$1,098.05	$1,098.30