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	$43.38	4.746%	$45.4388	$45.44	$45.45	$45.40
Purchase #2	$163.80	8.859%	$178.311	$178.31	$178.30	$178.30
Purchase #3	$162.30	5.547%	$171.3028	$171.30	$171.30	$171.30
Purchase #4	$215.32	3.509%	$222.8756	$222.88	$222.90	$222.90
Purchase #5	$221.70	7.535%	$238.4051	$238.41	$238.40	$238.40
Purchase #6	$244.60	11.339%	$272.3352	$272.34	$272.35	$272.30
Purchase #7	$97.57	12.656%	$109.9185	$109.92	$109.90	$109.90
7 purchase totals =	$1,148.67		$1,238.5870	$1,238.60	$1,238.60	$1,238.50