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	$173.37	11.400%	$193.1342	$193.13	$193.15	$193.10
Purchase #2	$169.78	12.491%	$190.9872	$190.99	$191.00	$191.00
Purchase #3	$34.47	7.303%	$36.9873	$36.99	$37.00	$37.00
Purchase #4	$241.64	9.382%	$264.3107	$264.31	$264.30	$264.30
Purchase #5	$102.46	13.736%	$116.5339	$116.53	$116.55	$116.50
Purchase #6	$176.52	13.649%	$200.6132	$200.61	$200.60	$200.60
Purchase #7	$154.72	10.856%	$171.5164	$171.52	$171.50	$171.50
7 purchase totals =	$1,052.96		$1,174.0829	$1,174.08	$1,174.10	$1,174.00