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	$160.41	10.362%	$177.0317	$177.03	$177.05	$177.00
Purchase #2	$80.69	10.847%	$89.4424	$89.44	$89.45	$89.40
Purchase #3	$207.62	11.668%	$231.8451	$231.85	$231.85	$231.80
Purchase #4	$12.67	8.171%	$13.7053	$13.71	$13.70	$13.70
Purchase #5	$227.78	4.689%	$238.4606	$238.46	$238.45	$238.50
Purchase #6	$231.95	9.317%	$253.5608	$253.56	$253.55	$253.60
Purchase #7	$12.47	11.308%	$13.8801	$13.88	$13.90	$13.90
7 purchase totals =	$933.59		$1,017.9260	$1,017.93	$1,017.95	$1,017.90