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	$104.86	7.683%	$112.9164	$112.92	$112.90	$112.90
Purchase #2	$228.65	3.130%	$235.8067	$235.81	$235.80	$235.80
Purchase #3	$138.48	3.784%	$143.7201	$143.72	$143.70	$143.70
Purchase #4	$168.55	12.854%	$190.2154	$190.22	$190.20	$190.20
Purchase #5	$242.48	11.704%	$270.8599	$270.86	$270.85	$270.90
Purchase #6	$59.29	6.332%	$63.0442	$63.04	$63.05	$63.00
Purchase #7	$27.56	4.713%	$28.8589	$28.86	$28.85	$28.90
7 purchase totals =	$969.87		$1,045.4216	$1,045.43	$1,045.35	$1,045.40