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	$63.33	8.203%	$68.525	$68.53	$68.55	$68.50
Purchase #2	$52.59	7.117%	$56.3328	$56.33	$56.35	$56.30
Purchase #3	$35.31	6.270%	$37.5239	$37.52	$37.50	$37.50
Purchase #4	$66.33	12.220%	$74.4355	$74.44	$74.45	$74.40
Purchase #5	$24.80	3.195%	$25.5924	$25.59	$25.60	$25.60
Purchase #6	$56.88	11.522%	$63.4337	$63.43	$63.45	$63.40
Purchase #7	$56.36	4.751%	$59.0377	$59.04	$59.05	$59.00
7 purchase totals =	$355.60		$384.8810	$384.88	$384.95	$384.70