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	$76.97	13.463%	$87.3325	$87.33	$87.35	$87.30
Purchase #2	$164.62	3.641%	$170.6138	$170.61	$170.60	$170.60
Purchase #3	$89.56	12.482%	$100.7389	$100.74	$100.75	$100.70
Purchase #4	$59.30	12.348%	$66.6224	$66.62	$66.60	$66.60
Purchase #5	$78.90	4.643%	$82.5633	$82.56	$82.55	$82.60
Purchase #6	$164.88	5.638%	$174.1759	$174.18	$174.20	$174.20
Purchase #7	$102.60	9.824%	$112.6794	$112.68	$112.70	$112.70
7 purchase totals =	$736.83		$794.7262	$794.72	$794.75	$794.70