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	$39.69	11.298%	$44.1742	$44.17	$44.15	$44.20
Purchase #2	$158.90	3.501%	$164.4631	$164.46	$164.45	$164.50
Purchase #3	$60.47	10.366%	$66.7383	$66.74	$66.75	$66.70
Purchase #4	$82.65	11.660%	$92.287	$92.29	$92.30	$92.30
Purchase #5	$96.31	4.236%	$100.3897	$100.39	$100.40	$100.40
Purchase #6	$55.73	9.782%	$61.1815	$61.18	$61.20	$61.20
Purchase #7	$219.99	7.581%	$236.6674	$236.67	$236.65	$236.70
7 purchase totals =	$713.74		$765.9012	$765.90	$765.90	$766.00