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	$78.92	10.641%	$87.3179	$87.32	$87.30	$87.30
Purchase #2	$141.37	9.281%	$154.4905	$154.49	$154.50	$154.50
Purchase #3	$147.62	13.838%	$168.0477	$168.05	$168.05	$168.00
Purchase #4	$23.73	7.276%	$25.4566	$25.46	$25.45	$25.50
Purchase #5	$72.88	7.113%	$78.064	$78.06	$78.05	$78.10
Purchase #6	$68.39	5.632%	$72.2417	$72.24	$72.25	$72.20
Purchase #7	$129.52	13.167%	$146.5739	$146.57	$146.55	$146.60
7 purchase totals =	$662.43		$732.1923	$732.19	$732.15	$732.20