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	$157.83	4.779%	$165.3727	$165.37	$165.35	$165.40
Purchase #2	$157.46	4.330%	$164.278	$164.28	$164.30	$164.30
Purchase #3	$94.92	4.309%	$99.0101	$99.01	$99.00	$99.00
Purchase #4	$80.51	12.607%	$90.6599	$90.66	$90.65	$90.70
Purchase #5	$119.31	11.184%	$132.6536	$132.65	$132.65	$132.70
Purchase #6	$63.39	10.564%	$70.0865	$70.09	$70.10	$70.10
Purchase #7	$36.43	11.648%	$40.6734	$40.67	$40.65	$40.70
7 purchase totals =	$709.85		$762.7342	$762.73	$762.70	$762.90