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	$160.95	4.704%	$168.5211	$168.52	$168.50	$168.50
Purchase #2	$218.73	3.268%	$225.8781	$225.88	$225.90	$225.90
Purchase #3	$153.90	4.563%	$160.9225	$160.92	$160.90	$160.90
Purchase #4	$151.79	11.128%	$168.6812	$168.68	$168.70	$168.70
Purchase #5	$237.56	6.535%	$253.0845	$253.08	$253.10	$253.10
Purchase #6	$102.55	7.211%	$109.9449	$109.94	$109.95	$109.90
Purchase #7	$113.53	6.160%	$120.5234	$120.52	$120.50	$120.50
7 purchase totals =	$1,139.01		$1,207.5557	$1,207.54	$1,207.55	$1,207.50