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	$65.67	10.440%	$72.5259	$72.53	$72.55	$72.50
Purchase #2	$86.40	4.616%	$90.3882	$90.39	$90.40	$90.40
Purchase #3	$17.97	11.303%	$20.0011	$20.00	$20.00	$20.00
Purchase #4	$114.63	9.282%	$125.27	$125.27	$125.25	$125.30
Purchase #5	$168.38	11.638%	$187.9761	$187.98	$188.00	$188.00
Purchase #6	$95.93	4.247%	$100.0041	$100.00	$100.00	$100.00
Purchase #7	$46.84	6.321%	$49.8008	$49.80	$49.80	$49.80
7 purchase totals =	$595.82		$645.9662	$645.97	$646.00	$646.00