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	$213.37	9.181%	$232.9595	$232.96	$232.95	$233.00
Purchase #2	$92.88	8.583%	$100.8519	$100.85	$100.85	$100.90
Purchase #3	$69.49	5.600%	$73.3814	$73.38	$73.40	$73.40
Purchase #4	$100.87	5.409%	$106.3261	$106.33	$106.35	$106.30
Purchase #5	$7.83	8.205%	$8.4725	$8.47	$8.45	$8.50
Purchase #6	$57.27	3.285%	$59.1513	$59.15	$59.15	$59.20
Purchase #7	$96.37	3.126%	$99.3825	$99.38	$99.40	$99.40
7 purchase totals =	$638.08		$680.5252	$680.52	$680.55	$680.70