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	$113.83	5.168%	$119.7127	$119.71	$119.70	$119.70
Purchase #2	$116.67	5.558%	$123.1545	$123.15	$123.15	$123.20
Purchase #3	$38.51	9.830%	$42.2955	$42.30	$42.30	$42.30
Purchase #4	$198.54	7.497%	$213.4245	$213.42	$213.40	$213.40
Purchase #5	$57.45	11.494%	$64.0533	$64.05	$64.05	$64.10
Purchase #6	$93.40	7.466%	$100.3732	$100.37	$100.35	$100.40
Purchase #7	$87.71	8.640%	$95.2881	$95.29	$95.30	$95.30
7 purchase totals =	$706.11		$758.3018	$758.29	$758.25	$758.40