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	$176.36	3.480%	$182.4973	$182.50	$182.50	$182.50
Purchase #2	$111.40	13.716%	$126.6796	$126.68	$126.70	$126.70
Purchase #3	$55.33	3.743%	$57.401	$57.40	$57.40	$57.40
Purchase #4	$229.55	8.389%	$248.8069	$248.81	$248.80	$248.80
Purchase #5	$41.42	7.360%	$44.4685	$44.47	$44.45	$44.50
Purchase #6	$239.40	10.205%	$263.8308	$263.83	$263.85	$263.80
Purchase #7	$81.97	12.589%	$92.2892	$92.29	$92.30	$92.30
7 purchase totals =	$935.43		$1,015.9733	$1,015.98	$1,016.00	$1,016.00