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	$56.78	9.784%	$62.3354	$62.34	$62.35	$62.30
Purchase #2	$249.25	6.444%	$265.3117	$265.31	$265.30	$265.30
Purchase #3	$138.48	12.575%	$155.8939	$155.89	$155.90	$155.90
Purchase #4	$155.61	11.487%	$173.4849	$173.48	$173.50	$173.50
Purchase #5	$226.30	3.751%	$234.7885	$234.79	$234.80	$234.80
Purchase #6	$71.49	12.547%	$80.4599	$80.46	$80.45	$80.50
Purchase #7	$241.48	5.280%	$254.2301	$254.23	$254.25	$254.20
7 purchase totals =	$1,139.39		$1,226.5044	$1,226.50	$1,226.55	$1,226.50