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	$31.62	5.623%	$33.398	$33.40	$33.40	$33.40
Purchase #2	$41.80	9.752%	$45.8763	$45.88	$45.90	$45.90
Purchase #3	$25.90	5.792%	$27.4001	$27.40	$27.40	$27.40
Purchase #4	$168.31	7.432%	$180.8188	$180.82	$180.80	$180.80
Purchase #5	$147.28	10.732%	$163.0861	$163.09	$163.10	$163.10
Purchase #6	$185.51	5.662%	$196.0136	$196.01	$196.00	$196.00
Purchase #7	$138.90	11.175%	$154.4221	$154.42	$154.40	$154.40
7 purchase totals =	$739.32		$801.0150	$801.02	$801.00	$801.00