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	$93.68	3.569%	$97.0234	$97.02	$97.00	$97.00
Purchase #2	$127.82	3.468%	$132.2528	$132.25	$132.25	$132.30
Purchase #3	$178.77	6.623%	$190.6099	$190.61	$190.60	$190.60
Purchase #4	$248.33	12.791%	$280.0939	$280.09	$280.10	$280.10
Purchase #5	$70.94	13.755%	$80.6978	$80.70	$80.70	$80.70
Purchase #6	$249.52	9.550%	$273.3492	$273.35	$273.35	$273.30
Purchase #7	$11.39	13.381%	$12.9141	$12.91	$12.90	$12.90
7 purchase totals =	$980.45		$1,066.9411	$1,066.93	$1,066.90	$1,066.90