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	$133.29	4.809%	$139.6999	$139.70	$139.70	$139.70
Purchase #2	$242.65	4.640%	$253.909	$253.91	$253.90	$253.90
Purchase #3	$126.86	5.812%	$134.2331	$134.23	$134.25	$134.20
Purchase #4	$35.94	6.212%	$38.1726	$38.17	$38.15	$38.20
Purchase #5	$145.52	4.778%	$152.4729	$152.47	$152.45	$152.50
Purchase #6	$47.94	3.382%	$49.5613	$49.56	$49.55	$49.60
Purchase #7	$190.46	10.455%	$210.3726	$210.37	$210.35	$210.40
7 purchase totals =	$922.66		$978.4214	$978.41	$978.35	$978.50