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	$107.69	6.274%	$114.4465	$114.45	$114.45	$114.40
Purchase #2	$120.91	5.490%	$127.548	$127.55	$127.55	$127.50
Purchase #3	$200.77	12.340%	$225.545	$225.55	$225.55	$225.50
Purchase #4	$233.77	5.215%	$245.9611	$245.96	$245.95	$246.00
Purchase #5	$54.52	6.815%	$58.2355	$58.24	$58.25	$58.20
Purchase #6	$40.32	7.618%	$43.3916	$43.39	$43.40	$43.40
Purchase #7	$57.99	13.311%	$65.709	$65.71	$65.70	$65.70
7 purchase totals =	$815.97		$880.8367	$880.85	$880.85	$880.70