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	$13.92	6.166%	$14.7783	$14.78	$14.80	$14.80
Purchase #2	$92.34	11.217%	$102.6978	$102.70	$102.70	$102.70
Purchase #3	$103.72	5.654%	$109.5843	$109.58	$109.60	$109.60
Purchase #4	$219.85	3.262%	$227.0215	$227.02	$227.00	$227.00
Purchase #5	$123.87	3.246%	$127.8908	$127.89	$127.90	$127.90
Purchase #6	$110.27	3.669%	$114.3158	$114.32	$114.30	$114.30
Purchase #7	$120.50	3.233%	$124.3958	$124.40	$124.40	$124.40
7 purchase totals =	$784.47		$820.6843	$820.69	$820.70	$820.70