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	$53.44	8.175%	$57.8087	$57.81	$57.80	$57.80
Purchase #2	$62.43	9.704%	$68.4882	$68.49	$68.50	$68.50
Purchase #3	$147.35	10.245%	$162.446	$162.45	$162.45	$162.40
Purchase #4	$177.84	6.514%	$189.4245	$189.42	$189.40	$189.40
Purchase #5	$166.39	8.603%	$180.7045	$180.70	$180.70	$180.70
Purchase #6	$126.67	7.414%	$136.0613	$136.06	$136.05	$136.10
Purchase #7	$200.78	11.815%	$224.5022	$224.50	$224.50	$224.50
7 purchase totals =	$934.90		$1,019.4354	$1,019.43	$1,019.40	$1,019.40