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	$102.67	11.839%	$114.8251	$114.83	$114.85	$114.80
Purchase #2	$158.32	7.478%	$170.1592	$170.16	$170.15	$170.20
Purchase #3	$172.50	4.428%	$180.1383	$180.14	$180.15	$180.10
Purchase #4	$63.98	3.347%	$66.1214	$66.12	$66.10	$66.10
Purchase #5	$198.47	9.740%	$217.801	$217.80	$217.80	$217.80
Purchase #6	$92.89	11.547%	$103.616	$103.62	$103.60	$103.60
Purchase #7	$171.88	10.870%	$190.5634	$190.56	$190.55	$190.60
7 purchase totals =	$960.71		$1,043.2244	$1,043.23	$1,043.20	$1,043.20