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	$79.69	4.446%	$83.233	$83.23	$83.25	$83.20
Purchase #2	$126.97	5.139%	$133.495	$133.50	$133.50	$133.50
Purchase #3	$84.77	6.861%	$90.5861	$90.59	$90.60	$90.60
Purchase #4	$86.50	8.619%	$93.9554	$93.96	$93.95	$94.00
Purchase #5	$25.71	6.116%	$27.2824	$27.28	$27.30	$27.30
Purchase #6	$123.77	11.364%	$137.8352	$137.84	$137.85	$137.80
Purchase #7	$61.51	6.835%	$65.7142	$65.71	$65.70	$65.70
7 purchase totals =	$588.92		$632.1013	$632.11	$632.15	$632.10