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	$112.61	9.149%	$122.9127	$122.91	$122.90	$122.90
Purchase #2	$93.69	10.418%	$103.4506	$103.45	$103.45	$103.50
Purchase #3	$119.49	11.751%	$133.5313	$133.53	$133.55	$133.50
Purchase #4	$160.27	11.283%	$178.3533	$178.35	$178.35	$178.40
Purchase #5	$113.70	12.399%	$127.7977	$127.80	$127.80	$127.80
Purchase #6	$73.76	7.527%	$79.3119	$79.31	$79.30	$79.30
Purchase #7	$112.59	9.820%	$123.6463	$123.65	$123.65	$123.60
7 purchase totals =	$786.11		$869.0038	$869.00	$869.00	$869.00