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	$103.30	9.314%	$112.9214	$112.92	$112.90	$112.90
Purchase #2	$48.27	11.239%	$53.6951	$53.70	$53.70	$53.70
Purchase #3	$48.69	3.773%	$50.5271	$50.53	$50.55	$50.50
Purchase #4	$120.75	5.726%	$127.6641	$127.66	$127.65	$127.70
Purchase #5	$134.40	6.318%	$142.8914	$142.89	$142.90	$142.90
Purchase #6	$225.77	12.445%	$253.8671	$253.87	$253.85	$253.90
Purchase #7	$136.66	3.668%	$141.6727	$141.67	$141.65	$141.70
7 purchase totals =	$817.84		$883.2389	$883.24	$883.20	$883.30