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	$76.41	11.643%	$85.3064	$85.31	$85.30	$85.30
Purchase #2	$161.25	4.790%	$168.9739	$168.97	$168.95	$169.00
Purchase #3	$160.35	3.582%	$166.0937	$166.09	$166.10	$166.10
Purchase #4	$113.27	13.374%	$128.4187	$128.42	$128.40	$128.40
Purchase #5	$95.25	9.699%	$104.4883	$104.49	$104.50	$104.50
Purchase #6	$188.39	5.854%	$199.4184	$199.42	$199.40	$199.40
Purchase #7	$79.84	3.123%	$82.3334	$82.33	$82.35	$82.30
7 purchase totals =	$874.76		$935.0328	$935.03	$935.00	$935.00