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	$135.62	13.831%	$154.3776	$154.38	$154.40	$154.40
Purchase #2	$203.56	13.621%	$231.2869	$231.29	$231.30	$231.30
Purchase #3	$68.82	6.855%	$73.5376	$73.54	$73.55	$73.50
Purchase #4	$127.92	10.777%	$141.7059	$141.71	$141.70	$141.70
Purchase #5	$100.91	8.606%	$109.5943	$109.59	$109.60	$109.60
Purchase #6	$213.92	10.741%	$236.8971	$236.90	$236.90	$236.90
Purchase #7	$78.67	3.151%	$81.1489	$81.15	$81.15	$81.10
7 purchase totals =	$929.42		$1,028.5483	$1,028.56	$1,028.60	$1,028.50