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	$180.69	13.359%	$204.8284	$204.83	$204.85	$204.80
Purchase #2	$39.85	4.863%	$41.7879	$41.79	$41.80	$41.80
Purchase #3	$46.25	5.559%	$48.821	$48.82	$48.80	$48.80
Purchase #4	$162.37	6.436%	$172.8201	$172.82	$172.80	$172.80
Purchase #5	$154.62	11.608%	$172.5683	$172.57	$172.55	$172.60
Purchase #6	$94.66	11.150%	$105.2146	$105.21	$105.20	$105.20
Purchase #7	$246.32	5.127%	$258.9488	$258.95	$258.95	$258.90
7 purchase totals =	$924.76		$1,004.9891	$1,004.99	$1,004.95	$1,004.90