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	$144.48	13.678%	$164.242	$164.24	$164.25	$164.20
Purchase #2	$58.47	7.241%	$62.7038	$62.70	$62.70	$62.70
Purchase #3	$138.34	7.686%	$148.9728	$148.97	$148.95	$149.00
Purchase #4	$171.38	6.696%	$182.8556	$182.86	$182.85	$182.90
Purchase #5	$129.34	4.778%	$135.5199	$135.52	$135.50	$135.50
Purchase #6	$150.27	9.840%	$165.0566	$165.06	$165.05	$165.10
Purchase #7	$226.33	10.719%	$250.5903	$250.59	$250.60	$250.60
7 purchase totals =	$1,018.61		$1,109.9410	$1,109.94	$1,109.90	$1,110.00