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	$119.95	6.478%	$127.7204	$127.72	$127.70	$127.70
Purchase #2	$200.70	4.181%	$209.0913	$209.09	$209.10	$209.10
Purchase #3	$230.33	6.666%	$245.6838	$245.68	$245.70	$245.70
Purchase #4	$37.38	7.736%	$40.2717	$40.27	$40.25	$40.30
Purchase #5	$73.85	6.698%	$78.7965	$78.80	$78.80	$78.80
Purchase #6	$40.29	8.407%	$43.6772	$43.68	$43.70	$43.70
Purchase #7	$176.55	13.714%	$200.7621	$200.76	$200.75	$200.80
7 purchase totals =	$879.05		$946.0030	$946.00	$946.00	$946.10