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	$38.43	12.759%	$43.3333	$43.33	$43.35	$43.30
Purchase #2	$246.84	6.520%	$262.934	$262.93	$262.95	$262.90
Purchase #3	$26.94	9.472%	$29.4918	$29.49	$29.50	$29.50
Purchase #4	$26.48	7.476%	$28.4596	$28.46	$28.45	$28.50
Purchase #5	$197.49	10.416%	$218.0606	$218.06	$218.05	$218.10
Purchase #6	$173.33	4.664%	$181.4141	$181.41	$181.40	$181.40
Purchase #7	$247.81	3.367%	$256.1538	$256.15	$256.15	$256.20
7 purchase totals =	$957.32		$1,019.8472	$1,019.83	$1,019.85	$1,019.90