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	$39.60	9.483%	$43.3553	$43.36	$43.35	$43.40
Purchase #2	$82.79	7.514%	$89.0108	$89.01	$89.00	$89.00
Purchase #3	$97.77	7.103%	$104.7146	$104.71	$104.70	$104.70
Purchase #4	$87.76	7.636%	$94.4614	$94.46	$94.45	$94.50
Purchase #5	$50.54	9.150%	$55.1644	$55.16	$55.15	$55.20
Purchase #6	$189.54	10.837%	$210.0804	$210.08	$210.10	$210.10
Purchase #7	$120.47	10.370%	$132.9627	$132.96	$132.95	$133.00
7 purchase totals =	$668.47		$729.7496	$729.74	$729.70	$729.90