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	$113.33	3.637%	$117.4518	$117.45	$117.45	$117.50
Purchase #2	$45.47	4.289%	$47.4202	$47.42	$47.40	$47.40
Purchase #3	$103.83	9.796%	$114.0012	$114.00	$114.00	$114.00
Purchase #4	$98.32	3.147%	$101.4141	$101.41	$101.40	$101.40
Purchase #5	$73.27	7.718%	$78.925	$78.93	$78.95	$78.90
Purchase #6	$72.48	10.810%	$80.3151	$80.32	$80.30	$80.30
Purchase #7	$38.55	13.416%	$43.7219	$43.72	$43.70	$43.70
7 purchase totals =	$545.25		$583.2493	$583.25	$583.20	$583.20