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	$203.85	5.682%	$215.4328	$215.43	$215.45	$215.40
Purchase #2	$140.55	5.626%	$148.4573	$148.46	$148.45	$148.50
Purchase #3	$164.89	13.662%	$187.4173	$187.42	$187.40	$187.40
Purchase #4	$101.90	4.643%	$106.6312	$106.63	$106.65	$106.60
Purchase #5	$100.67	11.860%	$112.6095	$112.61	$112.60	$112.60
Purchase #6	$103.90	6.658%	$110.8177	$110.82	$110.80	$110.80
Purchase #7	$134.45	9.303%	$146.9579	$146.96	$146.95	$147.00
7 purchase totals =	$950.21		$1,028.3237	$1,028.33	$1,028.30	$1,028.30