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	$85.55	5.605%	$90.3451	$90.35	$90.35	$90.30
Purchase #2	$105.93	3.394%	$109.5253	$109.53	$109.55	$109.50
Purchase #3	$182.76	12.641%	$205.8627	$205.86	$205.85	$205.90
Purchase #4	$123.37	4.372%	$128.7637	$128.76	$128.75	$128.80
Purchase #5	$209.40	3.262%	$216.2306	$216.23	$216.25	$216.20
Purchase #6	$38.94	9.149%	$42.5026	$42.50	$42.50	$42.50
Purchase #7	$144.83	5.801%	$153.2316	$153.23	$153.25	$153.20
7 purchase totals =	$890.78		$946.4616	$946.46	$946.50	$946.40