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	$135.59	6.789%	$144.7952	$144.80	$144.80	$144.80
Purchase #2	$209.92	7.622%	$225.9201	$225.92	$225.90	$225.90
Purchase #3	$180.38	11.718%	$201.5169	$201.52	$201.50	$201.50
Purchase #4	$83.90	12.380%	$94.2868	$94.29	$94.30	$94.30
Purchase #5	$153.28	4.864%	$160.7355	$160.74	$160.75	$160.70
Purchase #6	$187.84	4.824%	$196.9014	$196.90	$196.90	$196.90
Purchase #7	$35.25	10.337%	$38.8938	$38.89	$38.90	$38.90
7 purchase totals =	$986.16		$1,063.0497	$1,063.06	$1,063.05	$1,063.00