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	$49.49	5.690%	$52.306	$52.31	$52.30	$52.30
Purchase #2	$148.26	13.639%	$168.4812	$168.48	$168.50	$168.50
Purchase #3	$220.26	12.581%	$247.9709	$247.97	$247.95	$248.00
Purchase #4	$156.78	11.285%	$174.4726	$174.47	$174.45	$174.50
Purchase #5	$72.34	8.431%	$78.439	$78.44	$78.45	$78.40
Purchase #6	$177.90	10.451%	$196.4923	$196.49	$196.50	$196.50
Purchase #7	$13.99	4.278%	$14.5885	$14.59	$14.60	$14.60
7 purchase totals =	$839.02		$932.7505	$932.75	$932.75	$932.80