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	$193.65	8.727%	$210.5498	$210.55	$210.55	$210.50
Purchase #2	$193.40	3.671%	$200.4997	$200.50	$200.50	$200.50
Purchase #3	$231.42	10.332%	$255.3303	$255.33	$255.35	$255.30
Purchase #4	$28.65	10.280%	$31.5952	$31.60	$31.60	$31.60
Purchase #5	$119.75	3.451%	$123.8826	$123.88	$123.90	$123.90
Purchase #6	$30.34	12.181%	$34.0357	$34.04	$34.05	$34.00
Purchase #7	$5.71	7.236%	$6.1232	$6.12	$6.10	$6.10
7 purchase totals =	$802.92		$862.0165	$862.02	$862.05	$861.90