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	$180.54	5.414%	$190.3144	$190.31	$190.30	$190.30
Purchase #2	$48.83	9.549%	$53.4928	$53.49	$53.50	$53.50
Purchase #3	$11.42	7.432%	$12.2687	$12.27	$12.25	$12.30
Purchase #4	$148.60	5.274%	$156.4372	$156.44	$156.45	$156.40
Purchase #5	$117.33	7.756%	$126.4301	$126.43	$126.45	$126.40
Purchase #6	$164.49	13.303%	$186.3721	$186.37	$186.35	$186.40
Purchase #7	$50.85	4.323%	$53.0482	$53.05	$53.05	$53.00
7 purchase totals =	$722.06		$778.3635	$778.36	$778.35	$778.30