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	$132.31	13.260%	$149.8543	$149.85	$149.85	$149.90
Purchase #2	$77.56	6.256%	$82.4122	$82.41	$82.40	$82.40
Purchase #3	$50.76	5.279%	$53.4396	$53.44	$53.45	$53.40
Purchase #4	$139.90	13.180%	$158.3388	$158.34	$158.35	$158.30
Purchase #5	$199.42	7.239%	$213.856	$213.86	$213.85	$213.90
Purchase #6	$172.47	8.133%	$186.497	$186.50	$186.50	$186.50
Purchase #7	$55.61	4.177%	$57.9328	$57.93	$57.95	$57.90
7 purchase totals =	$828.03		$902.3307	$902.33	$902.35	$902.30