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	$156.77	8.166%	$169.5718	$169.57	$169.55	$169.60
Purchase #2	$106.68	12.222%	$119.7184	$119.72	$119.70	$119.70
Purchase #3	$118.78	7.245%	$127.3856	$127.39	$127.40	$127.40
Purchase #4	$241.28	7.534%	$259.458	$259.46	$259.45	$259.50
Purchase #5	$239.64	6.682%	$255.6527	$255.65	$255.65	$255.70
Purchase #6	$51.37	10.255%	$56.638	$56.64	$56.65	$56.60
Purchase #7	$150.31	7.787%	$162.0146	$162.01	$162.00	$162.00
7 purchase totals =	$1,064.83		$1,150.4391	$1,150.44	$1,150.40	$1,150.50