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	$85.87	5.308%	$90.428	$90.43	$90.45	$90.40
Purchase #2	$156.49	3.547%	$162.0407	$162.04	$162.05	$162.00
Purchase #3	$240.86	10.664%	$266.5453	$266.55	$266.55	$266.50
Purchase #4	$210.97	6.564%	$224.8181	$224.82	$224.80	$224.80
Purchase #5	$108.89	3.556%	$112.7621	$112.76	$112.75	$112.80
Purchase #6	$126.29	11.507%	$140.8222	$140.82	$140.80	$140.80
Purchase #7	$141.49	6.447%	$150.6119	$150.61	$150.60	$150.60
7 purchase totals =	$1,070.86		$1,148.0283	$1,148.03	$1,148.00	$1,147.90