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	$188.27	13.178%	$213.0802	$213.08	$213.10	$213.10
Purchase #2	$77.94	5.621%	$82.321	$82.32	$82.30	$82.30
Purchase #3	$229.78	11.293%	$255.7291	$255.73	$255.75	$255.70
Purchase #4	$63.50	8.775%	$69.0721	$69.07	$69.05	$69.10
Purchase #5	$180.48	8.777%	$196.3207	$196.32	$196.30	$196.30
Purchase #6	$108.65	10.245%	$119.7812	$119.78	$119.80	$119.80
Purchase #7	$108.39	9.702%	$118.906	$118.91	$118.90	$118.90
7 purchase totals =	$957.01		$1,055.2103	$1,055.21	$1,055.20	$1,055.20