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	$118.69	7.171%	$127.2013	$127.20	$127.20	$127.20
Purchase #2	$34.69	7.760%	$37.3819	$37.38	$37.40	$37.40
Purchase #3	$45.75	11.479%	$51.0016	$51.00	$51.00	$51.00
Purchase #4	$10.27	7.699%	$11.0607	$11.06	$11.05	$11.10
Purchase #5	$233.90	6.630%	$249.4076	$249.41	$249.40	$249.40
Purchase #6	$225.96	5.732%	$238.912	$238.91	$238.90	$238.90
Purchase #7	$75.81	7.861%	$81.7694	$81.77	$81.75	$81.80
7 purchase totals =	$745.07		$796.7345	$796.73	$796.70	$796.80