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	$48.70	9.127%	$53.1448	$53.14	$53.15	$53.10
Purchase #2	$134.47	5.366%	$141.6857	$141.69	$141.70	$141.70
Purchase #3	$82.61	8.634%	$89.7425	$89.74	$89.75	$89.70
Purchase #4	$192.99	12.355%	$216.8339	$216.83	$216.85	$216.80
Purchase #5	$133.98	9.595%	$146.8354	$146.84	$146.85	$146.80
Purchase #6	$249.72	4.846%	$261.8214	$261.82	$261.80	$261.80
Purchase #7	$179.83	4.189%	$187.3631	$187.36	$187.35	$187.40
7 purchase totals =	$1,022.30		$1,097.4268	$1,097.42	$1,097.45	$1,097.30