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	$162.39	8.337%	$175.9285	$175.93	$175.95	$175.90
Purchase #2	$35.54	8.173%	$38.4447	$38.44	$38.45	$38.40
Purchase #3	$112.25	4.639%	$117.4573	$117.46	$117.45	$117.50
Purchase #4	$31.40	11.734%	$35.0845	$35.08	$35.10	$35.10
Purchase #5	$184.95	6.113%	$196.256	$196.26	$196.25	$196.30
Purchase #6	$103.88	5.734%	$109.8365	$109.84	$109.85	$109.80
Purchase #7	$87.33	12.356%	$98.1205	$98.12	$98.10	$98.10
7 purchase totals =	$717.74		$771.1280	$771.13	$771.15	$771.10