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	$94.86	10.462%	$104.7843	$104.78	$104.80	$104.80
Purchase #2	$141.72	13.649%	$161.0634	$161.06	$161.05	$161.10
Purchase #3	$18.81	11.423%	$20.9587	$20.96	$20.95	$21.00
Purchase #4	$49.37	6.190%	$52.426	$52.43	$52.45	$52.40
Purchase #5	$73.85	6.607%	$78.7293	$78.73	$78.75	$78.70
Purchase #6	$146.30	10.543%	$161.7244	$161.72	$161.70	$161.70
Purchase #7	$140.55	5.235%	$147.9078	$147.91	$147.90	$147.90
7 purchase totals =	$665.46		$727.5939	$727.59	$727.60	$727.60