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	$66.76	5.857%	$70.6701	$70.67	$70.65	$70.70
Purchase #2	$248.75	11.787%	$278.0702	$278.07	$278.05	$278.10
Purchase #3	$29.90	5.586%	$31.5702	$31.57	$31.55	$31.60
Purchase #4	$141.70	11.142%	$157.4882	$157.49	$157.50	$157.50
Purchase #5	$233.90	9.120%	$255.2317	$255.23	$255.25	$255.20
Purchase #6	$206.97	4.492%	$216.2671	$216.27	$216.25	$216.30
Purchase #7	$38.91	11.600%	$43.4236	$43.42	$43.40	$43.40
7 purchase totals =	$966.89		$1,052.7211	$1,052.72	$1,052.65	$1,052.80