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	$158.37	12.481%	$178.1362	$178.14	$178.15	$178.10
Purchase #2	$48.94	11.552%	$54.5935	$54.59	$54.60	$54.60
Purchase #3	$57.73	6.683%	$61.5881	$61.59	$61.60	$61.60
Purchase #4	$216.83	7.768%	$233.6734	$233.67	$233.65	$233.70
Purchase #5	$34.84	11.526%	$38.8557	$38.86	$38.85	$38.90
Purchase #6	$98.99	3.586%	$102.5398	$102.54	$102.55	$102.50
Purchase #7	$131.78	7.676%	$141.8954	$141.90	$141.90	$141.90
7 purchase totals =	$747.48		$811.2821	$811.29	$811.30	$811.30