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	$58.51	4.786%	$61.3103	$61.31	$61.30	$61.30
Purchase #2	$184.26	10.631%	$203.8487	$203.85	$203.85	$203.80
Purchase #3	$214.53	13.607%	$243.7211	$243.72	$243.70	$243.70
Purchase #4	$19.31	7.785%	$20.8133	$20.81	$20.80	$20.80
Purchase #5	$57.97	8.346%	$62.8082	$62.81	$62.80	$62.80
Purchase #6	$43.85	4.605%	$45.8693	$45.87	$45.85	$45.90
Purchase #7	$76.59	7.526%	$82.3542	$82.35	$82.35	$82.40
7 purchase totals =	$655.02		$720.7251	$720.72	$720.65	$720.70