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	$75.59	3.376%	$78.1419	$78.14	$78.15	$78.10
Purchase #2	$114.36	11.494%	$127.5045	$127.50	$127.50	$127.50
Purchase #3	$179.62	9.376%	$196.4612	$196.46	$196.45	$196.50
Purchase #4	$122.59	6.341%	$130.3634	$130.36	$130.35	$130.40
Purchase #5	$36.94	12.617%	$41.6007	$41.60	$41.60	$41.60
Purchase #6	$198.39	10.588%	$219.3955	$219.40	$219.40	$219.40
Purchase #7	$186.91	8.649%	$203.0758	$203.08	$203.10	$203.10
7 purchase totals =	$914.40		$996.5430	$996.54	$996.55	$996.60