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	$160.48	13.714%	$182.4882	$182.49	$182.50	$182.50
Purchase #2	$123.65	7.608%	$133.0573	$133.06	$133.05	$133.10
Purchase #3	$69.86	12.272%	$78.4332	$78.43	$78.45	$78.40
Purchase #4	$63.81	5.328%	$67.2098	$67.21	$67.20	$67.20
Purchase #5	$45.58	13.767%	$51.855	$51.86	$51.85	$51.90
Purchase #6	$198.33	4.456%	$207.1676	$207.17	$207.15	$207.20
Purchase #7	$30.43	11.428%	$33.9075	$33.91	$33.90	$33.90
7 purchase totals =	$692.14		$754.1186	$754.13	$754.10	$754.20