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	$118.86	9.697%	$130.3859	$130.39	$130.40	$130.40
Purchase #2	$105.73	11.745%	$118.148	$118.15	$118.15	$118.10
Purchase #3	$33.64	11.328%	$37.4507	$37.45	$37.45	$37.50
Purchase #4	$138.35	3.484%	$143.1701	$143.17	$143.15	$143.20
Purchase #5	$116.44	4.824%	$122.0571	$122.06	$122.05	$122.10
Purchase #6	$5.59	5.718%	$5.9096	$5.91	$5.90	$5.90
Purchase #7	$218.31	5.163%	$229.5813	$229.58	$229.60	$229.60
7 purchase totals =	$736.92		$786.7027	$786.71	$786.70	$786.80