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	$111.78	9.613%	$122.5254	$122.53	$122.55	$122.50
Purchase #2	$184.89	12.736%	$208.4376	$208.44	$208.45	$208.40
Purchase #3	$95.69	6.478%	$101.8888	$101.89	$101.90	$101.90
Purchase #4	$94.89	6.452%	$101.0123	$101.01	$101.00	$101.00
Purchase #5	$162.71	3.298%	$168.0762	$168.08	$168.10	$168.10
Purchase #6	$75.38	10.823%	$83.5384	$83.54	$83.55	$83.50
Purchase #7	$145.94	8.838%	$158.8382	$158.84	$158.85	$158.80
7 purchase totals =	$871.28		$944.3169	$944.33	$944.40	$944.20