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	$112.66	5.833%	$119.2315	$119.23	$119.25	$119.20
Purchase #2	$94.93	9.150%	$103.6161	$103.62	$103.60	$103.60
Purchase #3	$60.66	9.106%	$66.1837	$66.18	$66.20	$66.20
Purchase #4	$206.69	13.368%	$234.3203	$234.32	$234.30	$234.30
Purchase #5	$231.47	12.268%	$259.8667	$259.87	$259.85	$259.90
Purchase #6	$78.84	4.798%	$82.6227	$82.62	$82.60	$82.60
Purchase #7	$127.52	11.119%	$141.6989	$141.70	$141.70	$141.70
7 purchase totals =	$912.77		$1,007.5399	$1,007.54	$1,007.50	$1,007.50