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	$46.35	13.420%	$52.5702	$52.57	$52.55	$52.60
Purchase #2	$174.88	8.332%	$189.451	$189.45	$189.45	$189.50
Purchase #3	$150.87	10.109%	$166.1214	$166.12	$166.10	$166.10
Purchase #4	$129.35	7.531%	$139.0913	$139.09	$139.10	$139.10
Purchase #5	$157.45	11.236%	$175.1411	$175.14	$175.15	$175.10
Purchase #6	$200.96	5.677%	$212.3685	$212.37	$212.35	$212.40
Purchase #7	$85.76	4.790%	$89.8679	$89.87	$89.85	$89.90
7 purchase totals =	$945.62		$1,024.6114	$1,024.61	$1,024.55	$1,024.70