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	$100.38	11.539%	$111.9628	$111.96	$111.95	$112.00
Purchase #2	$48.71	8.351%	$52.7778	$52.78	$52.80	$52.80
Purchase #3	$147.94	8.439%	$160.4247	$160.42	$160.40	$160.40
Purchase #4	$93.71	10.353%	$103.4118	$103.41	$103.40	$103.40
Purchase #5	$43.59	13.298%	$49.3866	$49.39	$49.40	$49.40
Purchase #6	$103.35	7.519%	$111.1209	$111.12	$111.10	$111.10
Purchase #7	$250.96	4.288%	$261.7212	$261.72	$261.70	$261.70
7 purchase totals =	$788.64		$850.8058	$850.80	$850.75	$850.80