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	$169.78	8.701%	$184.5526	$184.55	$184.55	$184.60
Purchase #2	$151.92	4.242%	$158.3644	$158.36	$158.35	$158.40
Purchase #3	$7.35	6.840%	$7.8527	$7.85	$7.85	$7.90
Purchase #4	$56.81	8.173%	$61.4531	$61.45	$61.45	$61.50
Purchase #5	$215.90	4.355%	$225.3024	$225.30	$225.30	$225.30
Purchase #6	$213.96	4.158%	$222.8565	$222.86	$222.85	$222.90
Purchase #7	$104.33	12.596%	$117.4714	$117.47	$117.45	$117.50
7 purchase totals =	$920.05		$977.8531	$977.84	$977.80	$978.10