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	$204.50	6.387%	$217.5614	$217.56	$217.55	$217.60
Purchase #2	$238.86	11.290%	$265.8273	$265.83	$265.85	$265.80
Purchase #3	$92.25	12.318%	$103.6134	$103.61	$103.60	$103.60
Purchase #4	$153.88	3.199%	$158.8026	$158.80	$158.80	$158.80
Purchase #5	$208.41	4.539%	$217.8697	$217.87	$217.85	$217.90
Purchase #6	$111.44	5.646%	$117.7319	$117.73	$117.75	$117.70
Purchase #7	$180.89	8.620%	$196.4827	$196.48	$196.50	$196.50
7 purchase totals =	$1,190.23		$1,277.8890	$1,277.88	$1,277.90	$1,277.90