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	$62.83	5.273%	$66.143	$66.14	$66.15	$66.10
Purchase #2	$118.48	12.205%	$132.9405	$132.94	$132.95	$132.90
Purchase #3	$11.96	12.668%	$13.4751	$13.48	$13.50	$13.50
Purchase #4	$233.48	13.690%	$265.4434	$265.44	$265.45	$265.40
Purchase #5	$84.30	6.284%	$89.5974	$89.60	$89.60	$89.60
Purchase #6	$237.93	5.321%	$250.5903	$250.59	$250.60	$250.60
Purchase #7	$232.53	10.823%	$257.6967	$257.70	$257.70	$257.70
7 purchase totals =	$981.51		$1,075.8864	$1,075.89	$1,075.95	$1,075.80