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	$95.31	3.139%	$98.3018	$98.30	$98.30	$98.30
Purchase #2	$39.53	9.720%	$43.3723	$43.37	$43.35	$43.40
Purchase #3	$62.31	4.840%	$65.3258	$65.33	$65.35	$65.30
Purchase #4	$151.62	9.837%	$166.5349	$166.53	$166.55	$166.50
Purchase #5	$198.41	11.680%	$221.5843	$221.58	$221.60	$221.60
Purchase #6	$160.85	3.359%	$166.253	$166.25	$166.25	$166.30
Purchase #7	$35.68	13.714%	$40.5732	$40.57	$40.55	$40.60
7 purchase totals =	$743.71		$801.9453	$801.93	$801.95	$802.00