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	$119.86	6.208%	$127.3009	$127.30	$127.30	$127.30
Purchase #2	$150.69	12.705%	$169.8352	$169.84	$169.85	$169.80
Purchase #3	$39.47	9.494%	$43.2173	$43.22	$43.20	$43.20
Purchase #4	$182.51	7.416%	$196.0449	$196.04	$196.05	$196.00
Purchase #5	$127.45	5.717%	$134.7363	$134.74	$134.75	$134.70
Purchase #6	$173.59	11.649%	$193.8115	$193.81	$193.80	$193.80
Purchase #7	$143.96	7.274%	$154.4317	$154.43	$154.45	$154.40
7 purchase totals =	$937.53		$1,019.3778	$1,019.38	$1,019.40	$1,019.20