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	$228.31	5.564%	$241.0132	$241.01	$241.00	$241.00
Purchase #2	$93.80	8.312%	$101.5967	$101.60	$101.60	$101.60
Purchase #3	$69.89	12.574%	$78.678	$78.68	$78.70	$78.70
Purchase #4	$78.90	4.245%	$82.2493	$82.25	$82.25	$82.20
Purchase #5	$231.72	10.296%	$255.5779	$255.58	$255.60	$255.60
Purchase #6	$232.73	7.524%	$250.2406	$250.24	$250.25	$250.20
Purchase #7	$136.56	10.256%	$150.5656	$150.57	$150.55	$150.60
7 purchase totals =	$1,071.91		$1,159.9213	$1,159.93	$1,159.95	$1,159.90